Gentaro Kisaragi

"Space is here!!!! Kamen Rider Fourze, let's settle this one-on-one!"

- pre-battle catchphrase

Kamen Rider Fourze (仮面ライダーフォーゼ) is the main protagonist in the series of Kamen Rider Fourze. His name roughly says Forty, as well as a combination of "Four" and "Zero", an indication of the Kamen Rider Series' 40th Anniversary and the forty different powers and weapons he can access with the Astroswitches.

Gentaro Kisaragi
'Gentaro Kisaragi (如月 弦太郎) is a second year student in Amanogawa High School, who has a delinquent Yankee-like appearance wearing a short jacket over a T-shirt and baggy pants, with his hair in a pompadour, rather than the clean cut uniform worn by other AGHS students; but is actually really friendly and wants to make friends with people in the school. He is willing to go the extra mile and do bizarre things to get to know someone he wants to befriend better. He puts friendship above anything else and values every friend that he has, to the point of crying hard whenever he hears a sad story of someone he considers a friend. He also has a special handshake he does with his friends and is commonly used when Gentaro makes a new friend. The reason he does so is because he wants to see that person he befriends smile, which is the best feeling one could have. He is generally very earnest and very thick-skinned, as well as not being very perceptive and at times, can actually be very dense. He is also prone to say things other people have a hard time comprehending, due to his unique and bizarre view in things. These quirky qualities are seen by others around him to be both annoying shortcomings and unusual strengths.

Gentaro lives with his grandfather Goro Kisaragi after his parents died in a traffic accident when Gentaro was in third grade. His parents had a job that (as Gentaro stated) went above both his and his grandfather's head, but they were always proud when their son made friends. His father also told him that he needed to keep his friends close because they would eventually help him out in the long run.

Gentaro is shown to become increasingly adept in using the Kamen Rider Fourze system as the series progresses. He is shown to only be able to use conventional fighting moves, and has to rely on Kengo's advice on which Astro switches to use in battle situations early in the series. As he gets increasingly used to fighting the Zodiarts, he learns how to devise strategies on the fly (though they do not always work and Kengo still needs to be around most of the time) and is seen to be using and changing Astro switches more often. He is shown to be very resourceful with the use of Switches as he learns how to utilize each one in unusual ways, such as using Limit Breaks of Launcher, Gatling and Fire Switches together to form a long range Limit Break finisher, and Limit Breaking the Rocket and Drill Switches twice when he cannot finish Scorpio off with just his usual Rider Rocket Drill Kick. When he has difficulty with properly using a Switch, he will take the time to understand it as he did with the Hopping Switch, ending up capable of using it as a weapon instead of just a tool.

History
After his parents died when he was in third grade, Gentaro was taken in by his grandfather Goro Kisaragi. The elder Kisaragi was a bike mechanic, and he and his grandson moved around a lot following the racing circuit (an experience Gentaro enjoyed) before moving back to the city where Gentaro initially lived with his parents. After reuniting with childhood friend Yuki Jojima, he tries to befriend loner Kengo Utahoshi, who goes out of his way to avoid him. When he slights Miu Kazashiro, Shun Daimonji begins to deal out "punishment" until a strange creature Yuki identifies as a Zodiarts appears. Gentaro begins to fight off the monster until Kengo arrives in the Powerdizer exo-suit, managing to keep the creature at bay, but leaving him physically drained. Kengo and Yuki head to an abandoned part of campus where they enter a locker that transports them to a lunar base known as the Rabbit Hatch. He prepares to use the devices left behind on the base, until Gentaro appears, having followed them into the locker. Gentaro takes the device from Kengo, who is still too tired to fight back. Gentaro faces off against the Zodiarts, but Yuki shows up to advise him on how to use the device he stole from Kengo. Gentaro activates the strange belt, transforming him into Kamen Rider Fourze for the first time. With Kengo's instruction, Gentaro is able to defeat the Zodiarts, and he is begrudgingly allowed to keep the Fourze Driver in order to battle the Zodiarts menace. To cement his new friendship, Gentaro forms a Kamen Rider Club, with Yuki and Kengo as its first members while taking up the title Kamen Rider.

During his second and third school year, Gentaro as Fourze would fight against the Zodiarts and their more powerful counterparts, the Horoscopes, gaining various Astro Switches along the way. He also meets another Kamen Rider who seeks the Aries Zodiarts, Kamen Rider Meteor. While their overall goals were different, Gentaro would see Meteor as a strong and powerful ally. When an exchange student from Subaruboshi High School, Ryusei Sakuta asks to join the Kamen Rider Club, Gentaro at first refuses as he saw through Ryusei's act in the fact he wasn't being himself in front of the club. He later accepts Ryusei into the club when he reveals a small part of his personality.

Eventually, the Kamen Rider Club learns that Ryusei's old school was infiltrated by the Horoscopes and heads there to deal with the situation. As Gentaro transforms to confront the Aries Zodiarts, he learns of his abilities and eventually manage to overpower him. However, just as Kamen Rider Fourze is about to finish the Zodiarts off, Kamen Rider Meteor intervenes and executes a Limit Break, followed by a one-inch punch on Kamen Rider Fourze, sending Gentaro into critical condition. Seeing Ryusei's blatant insubordination, Tachibana shuts down the Meteor system, effectively canceling Kamen Rider Meteor's transformation and revealing Ryusei's identity to the Kamen Rider Club. Gentaro dies shortly thereafter in front of all of them, after commending Ryusei for finally being true to Gentaro and to himself. However, with Tachibana's advice, Kengo managed to resurrect Gentaro with the Cosmic Switch using the bonds of friendship forged along thus far, gaining access to Cosmic States. With this new-found power, the Aries Zodiarts proves to be an easy opponent and is defeated shortly thereafter.

Gentaro once again displays the lengths he is willing to help a friend when the Capricorn Zodiarts, Tojiro Goto, shows up and convinces JK to reform their rock band named "Gene God", using the Capricorn Zodiarts powers to improve their musical talents as well as easily enthralling their audience. JK chooses to live his dream and quits the Kamen Rider Club, which results in Gentaro losing the use of Kamen Rider Fourze Cosmic States. Refusing to give up on a friend, Gentaro goes as far as to travel to JK's hometown ask JK's now-fisherman father to teach him the song JK heard growing up, just so that he can snap JK out and reminds him what it really means to chase one's dreams. Regaining JK's friendship shortly thereafter as well as the Cosmic States, Gentaro proceeds to make short work of the Capricorn Zodiarts.

Gentaro then befriended Erin Suda and Yuki receives a letter to join the Space International Development Agency's astronaut test, but Yuki is not alone, many other students also get the letter including Gentaro and Erin. During the first test, Gentaro meets the Aquarius Zodiarts who is intended to heal Kengo. Soon they both fight, but the pots on the Aquarius Zodiarts has the ability to heal herself. Learning that Erin is the Aquarius Zodiarts, Gentaro is confused of what happened. Erin says that she wants to become an astronaut like her father and be able to go into space, refusing to lose that honor to someone like Yuki. Gentaro made a promise if Yuki wins she must give her Aquarius Switch. However, Aquarius attacks once again although Fourze doesn't flinch on most attacks, the Zodiarts escapes once again. Gentaro learned that Yuki cheated, but he doesn't believe it. He then rushes to Erin and tell her to promise to be fair. Aquarius then fights Meteor Storm, but Erin remembers the promises that she has made. While on the moon Yuki tells Gentaro what happened on the second tests. In the survival race, Aquarius attacks Yuki, although learning Yuki helped Erin win. In the end, Gentaro is forced tofight Erin since they both can't be friends. Fourze successfully defeated Aquarius and because Erin's memories are erased, Gentaro (with Yuki) once again befriended Erin.

Later, Yuta Sugiura set Amanogawa School Bylaws, which prevent most students freedom. While Kengo, Yuki and Tomoko learning about Cosmic Energy form Professor Kuniteru Emoto, Gentaro, JK, and Ryusei make protests to Sugiura. Sugiura then beats Gentaro and JK in break dance and double dutch contests. As the Taurus Zodiarts' power is to make contracts and Gentaro and JK have sign in, Fourze can't punch Taurus. Gentaro and JK then change their appearance and become student council members. Gentaro then learns that Sugiura originally was for individuality before the previous president Sayaka Mibu warped his mind. Gentaro heads to the hospital where they find Sayaka, while Taurus takes the students' soul and turns them into drones.

Meanwhile, discussing what they learned from Sayaka on the conditions of her injury and his resulting mindset for his ideal justice, Gentaro stops Sugiura as he is about to punish Oki when he failed to let Tomoko escape. Gentaro then changes into Fourze but the contract is still in effect, using Foodroids to escape. Meteor Storm then appears and begins the challenge. Though Meteor wins, Taurus couldn't believe it and turns the Kamen Rider into his slave to help in capturing Oki as the students boxed her, Yuki, and JK into a corner. However, before the rest of the Kamen Rider Club is zombified, the Taurus Zodiarts sees smoke on the school rooftop and finds Sayaka having a fireworks barbecue. Gentaro then says what real justice is, then Sugiura breaks his Gu-anna and breaks out of his control. Gentaro is then enraged to see Taurus throw him to the Dark Nebula after the Virgo Zodiarts' offer declined and Taurus attacks her. Gentaro and Ryusei then change, but Virgo is too strong and the two lose.

After Virgo sends Tomoko into the Dark Nebula, she starts to intimidate all the Kamen Rider Club members, except for Gentaro, Kengo, and Ryusei. Gentaro tried to convince them back to the club, but no one wants to because they are scared of Virgo's attack. However, Tachibana arrived to aid Gentaro for using his ruthlessness to activate Cosmic States. Unfortunately, Gentaro couldn't do it, so Tachibana use a test to raise Gentaro's ruthlessness. Gentaro then succeeded the test in Rocket States when Tachibana told Gentaro to touch the pot that he prepared. But, soon enough, Kengo informed that Tachibana is Virgo. Ryusei becomes enraged and attacked Tachibana (as Virgo), only to be sent into the Dark Nebula. Kengo then suggests to Gentaro not to trust Tachibana, but still trusts him. On the next test, Gentaro must destroy the pot while it is held by Virgo. After Magnet States couldn't do it, when Virgo attacks, Fourze changes into Cosmic States as he then remembers that even if his friends die or become far from him, they're still beside him. Kamen Rider Club members also appear with Kengo, showing Virgo about friendship, she then brings back Ryusei and Tomoko and also reveals her identity as Kuniteru Emoto and the Dark Nebula's true destination, but he is attacked by the Sagittarius Zodiarts' arrow. Fourze and Meteor then fight Sagittarius, only to become punching bags for Sagittarius to show his power. All of the Kamen Rider Club then bury Emoto in the moon, after he is defeated by Libra and Leo, but he leaves some words to Kengo.

Yuki is then forced by Libra and Leo to press the Gemini Switch and split into two personae. One of them, Dark Yuki, starts to prank every KRC member. However, the real Yuki is the one tied up by Gentaro who tries to search for the Gemini Switch. After Yuki runs because Gentaro forgot what did Yuki gave him, Gentaro and Ryusei encounter the Gemini Zodiarts. As they are about to finish her off, Sagittarius appears and evolved Gemini into Gemini Nova as one of her attacks injures Ryusei. On that night, Dark Yuki takes Yuki's identity and the real Yuki started to become Dark Yuki. As her evil self throws the Gemini Switch to Yuki accidentally, she presses it. Dark Yuki provokes Gentaro to kill her, but Yuki escapes only to get caught by Gamou and Tatsugami to start the Star Luck Ritual. Gentaro then searches and finds the space ticket that he and Yuki made in their childhood. When Yuki starts to lose hope, Gentaro shows their ticket, giving her the strength to overcome her evil self. Gentaro then changes to Fourze and starts fighting the Gemini Zodiarts. After absorbing the explosion by using the Meteor Storm Switch from Ryusei, Fourze successively defeats Gemini and Yuki reverts back to normal. After that, all of the Kamen Rider Club members had their space tickets from Yuki.

Kamen Rider Fourze the Movie: Everyone, Space is Here!
In class, Gentaro is trying to make friends with his computer as Kengo, Yuki and Ryusei try to make him realize humans can't befriend machines. However this is interrupted as Ohsugi arrives to pull them out of class. On the Rabbit Hatch, the other Kamen Rider Club members have been summoned by Shizuka Shirayama who invites them to go to the OSTO Legacy (オスト・レガシー). While on their way to the headquarters, the convoy had been ambushed by Black Knight and Inga Blink (while riding a motorcycle) with Gentaro transforms into Fourze and fought Black Knight. Arriving at the OSTO Legacy headquarters, Harumi Saeba narrates while revealing a slideshow about the Space Ironmen Kyodain who are intending to use XVII'S laser beam to conquer Earth, and pleads the team to aboard a rocket to get into the satellite. They need the Kamen Rider Club to get aboard and and destroy XVII. Gentaro agrees to the mission, but believes he can befriend XVII rather than destroy it. Over the next several days, Kamen Rider Club undergoes intense astronaut training to get them ready for the mission. The night before, the gang discuss their upcoming adventure with Yuki excited about finally going into space. JK questions this, noting that they're on the moon all the time, but Yuki responds that it doesn't count unless they manage to escape the Earth's gravity the old fashioned way.

The next day, Gentaro realizes the ship which used to transport them to space was the same rocket that is Exodus (エクソダス) which Lem Kannagi used to go to space to transform into Super Galaxy King to fight him and OOO from their last confrontation. Shizuka explains this was the only craft they had available, and despite the misgivings, Gentaro and the others make to board the ship when they are suddenly blasted by all twelve Horoscopes marching towards them. Kengo scans them to find that, unlike the real Horoscopes, these ones aren't human but are rather solid cosmic energy. Gentaro and Ryusei decide to fight them off, as Shizuka warns the Exodus is run by computer and the countdown can't be interrupted, meaning Gentaro and Ryusei have a time limit to defeat the Horoscopes. As the rest of Kamen Rider Club are escorted to Exodus, Gentaro and Ryusei transform into Fourze and Meteor and take on their foes.

With Gentaro using the power of all forty Astro Switches and Ryusei using the Meteor Galaxy and Meteor Storm, they defeat the majority of the Horoscopes. However, they simply can't contend with all twelve and when Exodus is about to launch Sagittarius, Virgo, Gemini and Pisces are still remaining. Just when it seems like the two Kamen Riders are about to miss their flight, a strange black figure turns up and blasts the four. Gentaro asks the stranger who he is, and the man responds his name is Wizard, a meddling magician. Gentaro asks if he is a Kamen Rider, but Wizard is unfamiliar with the term. Gentaro explains that Kamen Riders fight enemies of humanity in secret. Wizard then decides to name himself "Kamen Rider Wizard". He offers to take care of the remaining Horoscopes, allowing Gentaro and Ryusei to make it to the Exodus at the last second.

On Exodus, Shizuka explains the mission specifics; they will separate into teams (Gentaro and Yuki, Ryusei and Tomoko, Kengo and Shizuka and Miu, Shun and JK). At four points aboard XVII, there are power cores that must be destroyed to disable XVII's beam before the brain can be shut down. With five hours to go, Shizuka wishes the team good luck and they prepare to head out.

However, they are ambushed again by Inga and Black Knight who are already aboard. Gentaro transforms to battle Black Knight, while Shun takes on the drones. Kengo asks about Shizuka's injury, but covers the wound and she shrugs it off before they continue on.

While walking through XVII, Yuki runs on ahead and trips over a part of the floor that raises and the iPad that she's carrying is thrown forward and explodes. Using the Smoke switch, Gentaro finds several laser beams which would have killed Yuki, if she didn't trip. Sadly reasoning that XVII can't really be befriended, Gentaro uses the Elek Switch to take out the lasers.

The rest of the team arrive on the Brain to shut it down, which Shizuka claims is the final part of the mission. Ryusei, Tomoko and Inga then turn up telling everyone else not to trust them, and Shizuka laughs while Harumi suddenly reveals himself (having stowed away on Exodus). The Kamen Rider Club realize they've been tricked, as the two reveal their true colours as they were using the Kamen Rider Club in order to fulfill their plan and transform into Space Ironmen Kyodain. Inga reveals to everyone that the Space Ironmen were created by her father Professor Blink but however an error occured causing two of them to went rogue and tries to revolt against humanity. In order to stop them, a dying Professor Blink actives XVII's Brain, activating a dampening field which trapped them in dormant human bodies. However, as the Kamen Rider Club has destroyed the field generators giving them all their powers back. Gentaro is distraught that he gave up on befriending XVII, especially when he realizes that XVII purposefully tripped Yuki up so she wouldn't run into the lasers from earlier. The Kyodains summoned Dustards to attack the Kamen Rider Club members as an angered Gentarou and Ryusei fight them.

Inga orders everyone to exit the satellite while she helps Fourze defeating them. As they were being overpowered by the Kyodains, both Gentarou and Ryusei dropped into the satellite's main core and the Kyodains program the satellite to transform into it's robotic form called One Seven Formation (ワンセブンフォーメーション) and launches a giant satellite beam to Earth while sending a message to Earth for humans to surrender or they'll destroy Japan. Gentarou and Ryusei awakes, realizing that XVII's Brain is using his probes to save them. Brain reveals that though the Kyodains had shutdown the Brain, but one of his probes are still functioning and transmitting his conciousness into it. Brain then states he will activate the self-destruct to stop the Ironmen, and Ryusei is ready to leave but Gentaro refuses; he's already wronged XVII once, he won't do it again. He makes Brain agree to halt the self-destruct until he has a chance to stop the laser.

Gentarou transforms into Fourze and use Cosmic States to transports the satellite to the moon via Limit Break, causing it to crash right next to the Rabbit Hatch. Although he's succeeded, when Fourze transports back to the satellite, the transformation is cancelled and all forty Astro Switches return to Rabbit Hatch and break from the overload. The Kyodains are enraged that their plan has been stopped, and knock the probe containing Brain before starting to give Gentaro and Meteor a severe beating, intending to kill the two before trying to fire again. XVII records and sends a recording about Ryusei fighting the Kyodains to the Rabbit Hatch.

However, with all of Fourze's Astro Switches damaged, they started to lose hope. Until XVII suddenly sends data to Kengo; a blueprint of a new switch which needs a massive amount of cosmic energy to form. Kengo knows it can be done, using the same method that was used to refine the Cosmic Switch; the power of friendship. What it requires is for all forty switches to be used at the same time by people who have strong feelings for Gentaro. Yuki suggests handing out the switches at Amanogawa High School. While Kengo and Inga stay behind and take a switch each (Kengo with Rocket and Inga with Flash), the others run into the school and start handing the switches out to the students, graduates and teachers whose lives have been touched by Gentaro's presence and everyone readily agrees to help their friend in trouble. Eventually, Yuki only has the Drill Switch left to deliver, and begins to wonder who she can give it to when Gamou arrives and offers to help. With the members of Kamen Rider Club also taking a switch each (Yuki takes Cosmic, Shun takes S Magnet, Miu takes N Magnet, Tomoko takes Fire and JK takes Elek), Yuki starts the countdown and everyone activates their switch. All the Astro Switches arrive at the Rabbit Hatch forming the new switch; the Fusion Switch. Kengo and Inga arrive just in time to deliver Gentaro the Fusion Switch which allows him to transform into Fourze. Gentaro then activiates the Fusion switch, which causes Ryusei to untransform as the Meteor switch travels to the Fourze driver which transforms Fourze into Meteor Fusion States, allowing him access to the powers of both Fourze and Meteor.

Fourze combines Meteor's Jeet Kun Do fighting style with his own and easily overpowers the Kyodains by using the Astro Switches and the Meteor Galaxy. Exhausted, the Kyodains transform into their vehicle form and combine it to defeat Fourze but he rides Machine Massigler combined with the Powerdizer to fight them. Reverting back to their Robot Form, the Kyodains combined their energy beams and shoot Fourze but however, Fourze himself uses Fusion Drill Rider Kick to destroy them. XVII thanks Fourze, and the two become friends before he flies back to space with the Kamen Rider Club members cheering on him.

Later, Inga and the members of Kamen Rider Club watch XVII blast into space with Gentaro giving the giant machine a friendship handshake before it goes.

With their adventure over, Kengo is amazed that Gentaro managed to befriend a machine however Tomoko isn't surprised as she feels nothing is impossible for him. Yuki asks Gentaro who he intends to befriend next, and Gentaro turns to the camera and (breaking the fourth wall) announces to the viewers that he'll befriend them all.

Later, on Kengo's birthday, Gentaro encounter Principal Kouhei Hayami who is protecting Ran Kuroki from becoming Pisces Zodiarts. Hayami reveals to the Kamen Rider Club that he is the Libra Zodiarts and the Day of Awakening. However, Hayami is attacked by Leo Zodiarts and can't transform because he gave the Libra Switch to Ryusei. Ran then presses Pisces Switch and transform into Pisces Zodiarts to save Hayami. Once Gentaro arrived, Gamou reveal that he is Sagitarrius Zodiarts and also defeats Fourze. Gentaro, Ryusei, and Hayami go to the Gamou base lair, only to be attacked by a Gemini clone. As Gentaro and Ryusei escape, Hayami tries to slow down the Gemini clone. At the same time, Leo kidnaps Haru to make the Pisces Switch change its color to red. As Pisces and Leo battle, Fourze arrived, but later it was revealed that it was Libra Zodiarts in disguise and the two defeat Pisces Zodiarts. Gentaro then arrives but sees that Hayami is faking all of the Kamen Rider Club members' trust, while Gamou performs Dark Nebula. As Meteor Storm battles Leo, Fourze attacks Sagittarius after Kengo is informed that using Dark Nebula weakened Sagittarius Zodiarts. However, Libra takes the final blow and is vaporized by the Dark Nebula's lightning. Kengo then uses the Core Switch's power to negate the Dark Nebula.

Kengo tells the Kamen Rider Club that he is the Core Child and he must meet the Presenters to stop Gamou's plan. At first Gentaro don't get it, but he must let his friend go to stop Gamou. At the Rabbit Hatch, Ryusei battles Tatsugami, who is trying to destroy the Rabbit Hatch. Gamou later arrives to aid the Leo Zodiarts, however Kengo pushed the Zodiarts away. Kengo then takes the Fourze Driver from Gentaro and leaves off to the Presenters, but he is killed by Sagittarius Nova who uses a Rider Kick-like attack to destroy the Core Switch. As all Kamen Rider Club members evacuate from Rabbit Hatch before it explodes, Yuki then reads Kengo's letter that he is leaving to meet the Presenters. Gentaro and Ryusei then rush to defeat Gamou. As Ryusei finally defeats Tatsugami, Fourze uses all of the States to battle Sagittarius Nova. After Fourze does a litte damage, he change into Cosmic State and the two perform Rider Kick. As the explosion occurs, Fourze uses the Barizun Sword to take Sagittarius to the AGHS. The remaining Kamen Rider Club members support Gentaro who battles Sagittarius Nova in human form. Gentaro then transforms once again and finally defeats Gamou. Gamou then tells Gentaro that he wanted to meet the Presenters, even if he must do bad things. However, Gentaro forgives Gamou and he accept Gentaro's friendship, but because Gamou used Sagittarius Nova, he began to vaporize. Gentaro and Yuki began remembering about Kengo and when Gentaro wanted to throw Kengo's letter, his hand is grabbed by Kengo. Kengo informs them, that Gamou used the Aquarius Switch power to fix the Core Switch. As Ryusei goes back to Subaruboshi High School and Ran and Haru join the Kamen Rider Club, Gentaro renames the club's name to the Space Kamen Rider Club, where their objective is to befriend the Presenters.

Movie War Ultimatum
"Saburo, you are my student!"

- Gentaro before battling Sanagiman as Fourze

5 years later, in Movie War Ultimatum, Gentaro has become one of the teachers in Amanogawa High School. He also became the advisor of the Space Kamen Rider Club. While trying to fix his hairstyle, Miyoko suddenly fell from her bike and Gentaro jumps from the window and grabs her in the nick of time. Miyoko thanked him for saving her with all of the students amazed at their teacher's action. During the class session, Gentaro brought a television which records his old friend, Yuki during her time at a space station. Saburo later uses his Gate powers and disturbs the class while declaring himself as the Leader of the Monster League along with his subordinates. Gentaro later seeks help from Mr. Ohsugi and Ms. Haruka to catch the misbehaving students as he chases after Saburo. Saburo later transforms into Sanagiman and fights Gentaro who has transformed into Fourze. Though Fourze finally overpowers Saburo with Fire States, but Kageto Banba interrupts and give Sanagiman his Zeber which amplify his sonic powers as Kageto strikes Fourze with his Kanabo as the Hercules Zodiarts. Meteor finally arrives and rescues Gentaro while saying that they must re-mobilize the previous members of the club in order to fight Kageto.

As the whole former members reunite, they infiltrate the Monster Leagues' base and explain to the members that they had been used as a key for Kageto Banba to create a sticker which will imitate their sonic ability for the black market. Realizing that his plan had been foiled, Kageto transforms into Hercules while summoning his Dustards to attack the Monster League and the Space Kamen Rider Club members with. Gentaro later chases Hercules but Sanagiman prevents him as he is still on Kageto's side. He explains to Gentaro that he had a horrible childhood which had made him use his powers as a protection from bullies. Gentaro tries to gain Sanagiman's trust, even by destroying the Fourze Driver as a sign of trust. With Meteor overpowered by Hercules, Sanagiman appears in front of Hercules and transforms into Inazuman. Miyoko later asks her teacher what happened to Saburo with Gentaro replying that after gaining his sense of justice, Sanagiman reappears as his true form, Inazuman. After Inazuman defeated the Hercules Zodiarts, he reverts back to his human form with Miyoko covering her eyes as Gentaro and Kengo realized that Saburo is naked and uses the Space Kamen Rider Club flag to cover him. Gentaro and everyone witness that an escape pod is entering the Earth as Kengo identifies it as Yuki's. But however, Eel interferes and destroys the escape pod with Kageto's laser beam tower. As everyone watches in horror, however, Kamen Rider Nadeshiko reappears, revealing that she was brought to Earth by Yuki and rescued her from the escape pod's destruction. Nadeshiko later uses her Rider Kick and destroys the laser beam tower. Eel tries to escape by creating a portal which brought him back to the present as Gentaro, Ryusei and Nadeshiko follows him. Gentaro bumps into his past self and asks him to lend him the Fourze Driver.

As Fourze, Meteor, and Nadeshiko arrive at the Infinite Monster Plant, they encounter and fought some monsters. When Koyomi started to lose hope, Fourze tells her that he is Wizard's friend and he will save him. He uses the Fourze Engage Ring and enters the Gate's Underworld along with Meteor and Nadeshiko. Arriving where Wizard is, he helps him defeat some monsters. After the fight, Gentaro, Ryusei, Nadeshiko, and Haruto arrive to where the Monster Army are and started to fight them in their human form. As Haruto summoned Accel, Double, Birth, and OOO thanks to the children, they transform and chase the armed car with their bikes. After the other Riders manage to get rid of the monsters on the vehicle, he enters the vehicle along with Wizard and fought the Akumaizer and defeated Eel and Gahra. As the other Riders destroy the vehicle with their Rider Kicks, Fourze and Wizard along with Poitrine evacuate as the summoned Riders disappear. The Riders were happy that the battle is over, until Xatan appears retrieving the Zeber as the armed car changes into Zaiderbeck. Fourze uses the Fusion Switch to change into Meteor Nadeshiko Fusion States while Wizard receives a new ring from Poitrine to change into Special Rush. As the two Riders change into their new Forms, they started to attack Zaiderbeck before landing on the Ocean of Magic. After Zaiderbeck is damaged, both Riders perform their Rider Kicks and defeat Xatan. After the battle, the Riders exit out of the Gate's Underworld. Gentaro asks Haruto to return the Fourze Driver to his past self and Haruto uses the Time Ring to return Gentaro and his friends to their time. Sometime later in the future, Gentaro took a class photo as the former members are wondering what will happen to Fourze. Back in the present time, Haruto returns the driver to the present Gentaro as he was shocked how he knew about him. After returning the belt, Haruto does the friendship handshake to Gentaro and gives him the Fourze Engage Ring.

Super Hero Taisen Z
Fourze appeared in Kamen Rider × Super Sentai × Space Sheriff: Super Hero Taisen Z. He joined with Kamen Riders Meteor, Decade, Super-1 and Space Sheriff Gavan Type G, as well as the Super Sentai teams Choushinsei Flashman and Tokusou Sentai Dekaranger, as the three forces of super heroes confronted Space Shocker.

Kamen Rider Wizard
Fourze is summoned with Kamen Rider W to protect the kids from being attacked.

All Rider Generation 1 & 2
Kamen Rider Fourze appears as a Hidden Rider in All Kamen Rider: Rider Generation video game as he can be unlocked by password. In the All Kamen Rider: Rider Generation 2‏‎, he appears as the main heroes along with Meteor.

Kamen Rider Climax Heroes Fourze and Super Climax Heroes
Kamen Rider Fourze appears in the video game Kamen Rider Climax Heroes Fourze and Kamen Rider Super Climax Heroes, in Climax Heroes Fourze, he only could access States until Fire States. In Super Climax Heroes, he can use all States sans Rocket and Clear Drill.

Kamen Rider Battride Wars
Kamen Rider Fourze appears as a Main Rider in the video game Kamen Rider Battride Wars, which unites the riders of the Heisei era from Kuuga to Wizard''. ''In order to recover his memories, Fourze must re-live his final battle against the Sagittarius Zodiarts, which frees him from his imprisonment.

In the game, Fourze's Base states has access to all his weapon type Switches in dons of Dynasty Warriors chaining style. Elek State is well-known hard hitter type form, which can perform special radial attack (Rider Ten Billion Volt Blast also used for aerial attack version) and 3-string normal aerial attacks (much like Agito Ground Form, Double (original (Joker Half-Changes) and FangJoker sides), Kiva Kiva Form, and Meteor).

Kamen Rider Fourze
The arsenal of Kamen Rider Fourze was developed by Rokuro Utahoshi who was a part of the Over Space Technology Organization. The OSTO developed technology that enables its user to harness a mysterious form of energy called Cosmic Energy. Rokuro was inspired by his visit to Kyoto and used a hypothetical system its occupants used in ancient times to model the Kamen Rider Fourze system after the Four Chinese Cardinal Guardians as reflected in the specific symbols on the Kamen Rider's limbs: Byakko the White Tiger (白虎), Suzaku the Vermillion Bird (朱雀), Seiryū the Azure Dragon (青竜), and Genbu the Black Tortoise (玄武). As hinted at by a message by Rokuro, the driving force behind the Fourze System are the bonds of friendship. Thus, not only is Gentaro the best suited to be Kamen Rider Fourze due to his ideals and bonds, but the friends he makes in creating the Kamen Rider Club enables Gentaro to bring out the true potential of Kamen Rider Fourze.

After Gentaro flips the four Switches on the Fourze Driver, he pulls the lever on the side of his belt, which transforms him into Kamen Rider Fourze. Gentaro took the equipment to become Kamen Rider Fourze from Kengo after he followed Kengo. Fourze is based off a space craft and roughly the retired Space Shuttle. Gentaro tends to say "Space is Here!" (宇宙キター) when transforming into Kamen Rider Fourze and says "Let's settle this once and for all!" (タイマン張らせてもらうぜ！) before battle.

Similar to his predecessors, Kamen Riders Double and OOO, Fourze uses combinations with the Astroswitches and their Modules. However, unlike the Gaia Memories and Core Medals, which need a certain combination to transform into different true forms, only a few of the Astroswitches changes Fourze into a different form (known as 'States'). Kamen Rider Fourze has shapes on his limbs where the Modules attach: Circle for the right arm, Cross for the right leg, Triangle for the left leg, and Square for the left arm. The suit itself also doubles as a spacesuit, allowing Kamen Rider Fourze to spacewalk. It also has a hover pack, allowing Kamen Rider Fourze to hover in the air for a short distance.

Mitsuaki Gamou once compared Kamen Rider Fourze's power to that of a gravitational lens, particularly on how the Kamen Rider influences both Astroswitches and Zodiarts Switches. After accepting the title of Kamen Rider, he often names his attacks with "Rider" before it.

States
Kamen Rider Fourze's forms are referred to as States (ステイツ).

Kamen Rider Fourze Base, Elek, and Fire States' ending theme is entitled "Giant Step".

Devices

 * Fourze Driver - Transformation device
 * Astroswitches - Fourze's (normally) small devices that allow him access to that Switch's Module when activated in the Driver
 * NS MagPhone - Fourze's cellphone-like gadget that allows the transformation into Magnet States
 * Elek Module Billy the Rod - Fourze's sword-like weapon that is used in Elek States through the Elek Switch
 * Fire Module Hee-Hackgun - Fourze's gun/flamethrower/fire extinguisher-like weapon that is used in Fire States through the Fire Switch
 * Cosmic Module Barizun Sword - Fourze's broadsword/club-like weapon used in Cosmic States and Fusion States

Vehicles

 * Machine Massigler - Fourze's Rider Machine
 * Powerdizer - An independent support vehicle to assist Fourze.

Appearances

 * Kamen Rider OOO Wonderful: The Shogun and the 21 Core Medals (early-bird cameo)
 * Kamen Rider Fourze
 * Episode 1 - Episode 48
 * Kamen Rider × Kamen Rider Fourze & OOO: Movie War Mega Max
 * Kamen Rider Fourze × Crayon Shin-chan
 * Kamen Rider × Super Sentai: Super Hero Taisen
 * Kamen Rider × Super Sentai: Super Hero Taihen – Who’s the culprit?!
 * Kamen Rider Fourze Hyper Battle DVD: Rocket Drill States of Friendship
 * Kamen Rider Fourze Special Bonus DVD: Astroswitch Secret Report 
 * Kamen Rider Fourze the Movie: Everyone, Space is Here!
 * Kamen Rider × Kamen Rider Wizard & Fourze: Movie War Ultimatum
 * Kamen Rider × Super Sentai × Space Sheriff: Super Hero Taisen Z (voice only as Kamen Rider Fourze)

Quotes

 * How can I befriend the entire school if I can't befriend scum like you? - say Gentaro to Kengo
 * Space is HEEEEEEEERE!! Kamen Rider Fourze! Let's do this man to man! - Before battling against Zodiarts.
 * I am Gentaro Kisaragi! I'm the man that will make all students become my friends - Gentaro when introducing himself.
 * Ryusei, I think this is the first time you are honest with me - Gentaro to Ryusei before his death.
 * Our bonds of friendship will take on the universe! - Gentaro typically after going Cosmic States

Portrayal
Gentaro Kisaragi is portrayed by Sota Fukushi (福士 蒼汰). As a child, Gentaro is portrayed by Tatsuki Ishikawa (石川 樹).

As Kamen Rider Fourze, his suit actor is Seiji Takaiwa (高岩 成二), who has been the suit actor for the majority of leading Heisei Kamen Riders.

Etymology
If one were to remove certain letters in Gentaro Kisaragi's name, and then rearrange them, it would say Stronger.

Trivia

 * Fourze is the second main Kamen Rider whose theme revolves on space. The first one was his Showa counterpart Kamen Rider Super-1.
 * Also, Fourze's helmet resembles Skyzel from Uchuu Tetsujin Kyodain.
 * He is the first Kamen Rider to have white as the main color for base form.
 * Fourze's Magnet States is similar to Kamen Rider Gatack's Masked Form, as they both have shoulder-mounted cannons.
 * The Switching Lung on Cosmic States is a touch screen-like device, similar to the K-Touch from Kamen Rider Decade.
 * His personality is similiar to that of (MegaRed) from , as they are both carefree high school slackers.
 * Coincidentally, as seen in Kamen Rider × Kamen Rider Wizard & Fourze: Movie War Ultimatum, Gentaro eventually became a teacher at Amanogawa High School, just as Kenta was shown to have become a teacher at his old high school, when he reappeared in .
 * Also of coincidence, Megarangers American adaptation, ', had a pure space theme (while the space-themed mecha originated in Megaranger, the Sentai's motif was electronics and video games), much like Fourze''.
 * The shapes on Fourze may seem like just simple shapes (not to mention highly coincidental), but the order of them relates to how they are drawn: a circle is one line in a loop, a cross is two crossed lines, a triangle is three connected lines, and a square is four connected lines.
 * Gentaro is the youngest main protagonist Kamen Rider to date, being only a second year high school student when he debuted and a third year after his final victory.
 * Gentaro is the second Rider to use what is normally a movie-exclusive power within the main series. The first being Shotaro Hidari.
 * In Kamen Rider × Kamen Rider Fourze & OOO: Movie War Mega Max, Philip mentions that Gentaro looks similar to his partner, Shotaro Hidari.
 * As of Kamen Rider × Super Sentai: Super Hero Taisen, Gentaro is the first rider to pilot a Super Sentai Robo (Go-Buster-Oh).