Sougo Tokiwa

Sougo Tokiwa (常磐ソウゴ), alternatively spelt Sogo Tokiwa, is an 18-year-old high school student who is visited by Tsukuyomi and Woz from 50 years in the future and learns that he is destined to become the tyrannical ruler of their time, Oma Zi-O. With this knowledge, he makes it his goal to be a great king through kindness by becoming Kamen Rider Zi-O (仮面ライダージオウ). However, Geiz Myoukouin is hellbent on killing him to alter the course of history.

History
Sougo Tokiwa was born on April 28, 2000. Living with his grand-uncle Junichiro in a clock shop, he attended high school at Hikarigamori High School, excelling in history but poor in physics. From an early age, Sougo had a dream that Dai Mazines were attacking and destroying the city, only to be saved by a mysterious man who told him that the impending crisis can be averted if he becomes a king. Since then, Sougo believed that he would become a king, much to the consternation of his uncle and his friends’ chagrin.

The Birth of Zi-O
One day, Sougo found a mysterious watch-like item that was on the seat of his bicycle, and after examining the blank item, Sougo laid down the blank item, then went on home while minding his own business l. Later while bicycling down a small street up towards a stairway, a man in hood, holding a grimoire appeared out of nowhere, who told him that it would be a momentous day for him and to avoid the "red robot" before mysteriously disappearing.

He does indeed encounter the robot shortly after, run by a man in red and black attire and attacks Sougo. He is saved by a woman claiming to be from the future named Tsukuyomi in her Time Mazine. They seemingly travel back in time to 1671 Japan where she proves her legitimacy to him. Tsukuyomi warns Sougo that the watch he currently had possessed a tremendous amount of power and using it will make Sougo turn into the worst and lowest demon king, Oma Zi-O. Just before Sougo could reply, a fight occurs and Tsukuyomi decide to test whether Sougo is really Oma Zi-O or not by forcefully putting Sougo in the middle of the fight. The citizens proceed to throw Sougo to a river and doing so makes peace for themselves. Instead of lamenting his misfortune, Sougo is relieved to see that the group had reconciled, much to the citizens’ amusement. However, a red Kamen Rider, Geiz manages to tail them and the two retreat back into the Time Mazine.

When Tsukuyomi was being attacked by Geiz, Sougo gets kicked out of the mech and wakes up in a strange world with a huge wall in the horizon. As he ponders over this, a Smash attacked him but luckily Kamen Riders Build and Cross-Z appears to help. After revealing their names, Sento and Ryuga bring Sougo to the cafe Nascita.

As Ryuga drinks from a carton of milk, Sougo sees the expiration date and realized that he's indeed in the year 2017. Sento affirms that Sougo is indeed from the future since, after some analysis, Sougo's Ridewatch is different from any current technology. Before Sento can ask about the future, Tsukuyomi appeared and shot the three of them into unconsciousness using Faizphone X, in order to prevent Sougo from interfering with the past any more than necessary. He wakes up in his old home, believing it to be all a dream. Later, he encounters a monster with the similar look of Kamen Rider Build attacking civilians. He tries to stop him but is quickly subdued twice.

Sougo was approached by the prophet, Woz once again, who then tells him that he'll become an demonic king who will reign over the future. Tsukuyomi desperately tries to warns Sougo to not use the Ridewatch. However, after some quick thought, Sougo decides to not become a tyrant, but to become a beloved demonic king of the future, much to both Tsukuyomi and Woz’s surprise. After that, the blank Ridewatch revealed itself to becoming the Zi-O Ridewatch, then Sougo is given the Ziku-Driver by Woz to transform and battle the elusive Kaijin Rider. As it is his new beginning of becoming a Kamen Rider, Woz announced the introduction of Sougo as he was now Kamen Rider Zi-O, the King of Time, much to Tsukuyomi’s disappointment.

He is able to go on par with Another Build and is quick to defeat him using the Zikan GiLade finisher. Geiz enters the fray, seemingly frustrated with Sougo on his decision and Tsukuyomi as she failed in convincing him. Geiz proceeds to ask why Sougo became Zi-O, which the latter replied that it was probably decided from the moment he was born. Reminiscing Oma Zi-O’s declaration, Geiz deems Sougo as irredeemable and transforms using both Geiz and Ghost Ridewatchs to become Kamen Rider Geiz GhostArmor and advances towards Zi-O.

Assisting the Genius Physicist & Obtaining Build's Power
Geiz proceeds to attack Zi-O relentlessly until Tsukuyomi piloting the Time Mazine and tells Zi-O to run. After a lenghty bike chase, he manages to do so. Sougo then encounters Woz once more, who formally introduces himself. He states that the two that hail from the future are trying to change the future. Woz then warns him a group named the Time Jackers who have the same goal but to have another king of their choosing in the future. He claims to be the one keeping the timeline the same and that he's on Sougo’s side, remarking that his conquest has only just begun. He later finds Another Build fighting Geiz and rescues the two. With his Time Break, Zi-O seemingly defeats the monster once more, only to find it again within seconds. Believing the real Build could defeat him, he rushes off to find him.

Later, Sougo went to the same cafe to meet Sento and Ryuga again. However, due to Another Build's appearances, Nascita's scenery had changed, the fridge that was the passway to the Build laboratory is gone and both Sento and Ryuga become Tsunagizu fanboys instead, seemingly forgetting their memories of being Kamen Riders and their encounter with Sougo the previous year. After Geiz destroys Another Build once again, Sento and Ryuga memories returned, and two blank-ridewatches that they somehow possessed turns into the Build and Cross-Z Ridewatches. Sento then said to Sougo to take care of his past self and gives him the Build and Cross-Z Ridewatches. Although he doesn't understand at first, he quickly realizes that Another Build showed up and attacked Sento and Ryuga in 2017 and Sougo went back in time to help defeat it. He meets up again with Geiz and Tsukuyomi informing them and the two Riders head to their Time Mazines and head back to the past.

Sougo and Geiz manage to arrive at the very scene, only to be interrupted by Uhr of the Time Jackers. He tells Sougo that the host of Another Build's fate was to have his athletic career abruptly ended in an accident and that he helped him move forward. The latter argues that despite his ability to time travel and intervene with other's lives, it's that individual that can determine his or her future. Impressed with his statement, Uhr wonders what "his" future will look like and walks away. The two Riders transform and join up with Build and Cross-Z to take down Another Build. However, the change of events in the timeline has caused Build's and Cross-Z's powers to disappear, seemingly to have transferred into the Cross-Z and Build Ridewatches. Zi-O uses the Build Ridewatch to become Zi-O BuildArmor, with Woz appearing and remarking this moment. Zi-O Build Armor now able to damage the monster, with Geiz subduing him with his Zikan Zax in Yumi Mode. Zi-O uses Vortex Time Break to finish the monster with Geiz utilizing the Zax's finisher equipped with the Cross-Z ridewatch. Remembering that Sento and Ryuga gave Sougo the Ridewatches, he asks the two to hold on to two blank Ridewatches for safe keeping. Sento corrects him by saying that his real name is Takumi Katsuragi, and he seems to forget about Sougo. Geiz demands to know what's with sudden anomalies in the timeline, but Sougo himself is confused about it as well, only exclaiming that Sento and Ryuga will choose to become Kamen Rider Build and Cross-Z in the future.

Sougo wakes up the next morning to find out that Tsukuyomi and Geiz have rented out that his uncle's spare rooms. Tsukuyomi explains that him saving the two has questioned whether or not he will grow to become a vile dictator and have decided to keep an eye on him, with Geiz later saying his vendetta towards him hasn't ceased. Despite all this, Sougo seems to be fine with the two living under the same roof as him.

Genius Gamer M & Obtaining Ex-Aid's Power
The first day that Geiz and Tsukuyomi took a class with Sougo, Sougo didn't feel relax a bit because whatever he did, they would follow and sneak on him, especially Geiz took a look at him closely when he was about to use the toilet. During the lunchtime, he hid inside the sport warehouse and met a student playing a game from GENM Corp, similar to Mighty Action X game. However, when Sougo tricked the gym teacher for covering the student to play the game in quiet, Another Ex-Aid appeared and attacked the player. Sougo transformed and fought it, but after he got thrown, Another Ex-Aid disappeared. Geiz and Tsukuyomi came to Sougo and explained that it wasn't his fault and Another Rider had appeared.

At home, Sougo thought to play the game to lure Another Ex-Aid, but his skill was beyond help as he couldn't reach the level where the student would be attacked. Tsukuyomi said about if only there was a gamer which could help as even she and Geiz couldn't play any old video game, Sougo rushly caught an idea to search a gamer and went to search for Genius Gamer M after Tsukuyomi took a look on her history tablet. Sougo late to realize if doing things like running around to search for him was 100% a difficult task but he got tired after he had done that. But he found another victim and Another Ex-Aid escaped in a blink, with Sougo couldn't even reaching for it. Woz came and told Sougo to take the victim to the doctor.

Sougo, Geiz, and Tsukuyomi took the victim to Seito hospital. There, Sougo heard of a doctor who played games with the name of Emu and asked where he was. Hiiro met them and asked about the ruckus and Sougo told him of what he wanted. Hiiro recalled about Emu was missing after he played the mentioned game after Sougo revealed that the incident of the disease was related to the game. There was a note and Hiiro as he claimed that he somehow could trust them, on playing the game. The note was written in the German language and Geiz able to read it, revealing that it was a code for the player when they played the game. Sougo realized the meaning of the code after Geiz translated it and played the game, making them to be dragged to the game world itself and encountered Another Ex-Aid.

Sougo and Geiz transformed and fought Another Ex-Aid, who proved formidable until they transformed into Zi-O Build Armor and Geiz Drive Armor respectively to defeat it. Emu appeared and congratulated them on cracking his code in a cold tone, before transforming into Ex-Aid and attacking them.

Reaching the Stars & Obtaining Fourze's Power
In 2018, Sougo finds out that several high school girls are missing, and Tsukuyomi mentions that an Another Rider is maybe behind this. Sougo, Tsukuyomi, and Geiz then go to Amanogawa High School, where the last victim last seen. Indeed, in there they met Another Fourze attacking a girl. After repelling the kaijin, Sougo and co. are forced to go to the Kamen Rider Club. The club's temporary advisor, Chuta Ohsugi then gives Sougo the Fourze Ridewatch, that he got from the club's official advisor.

King Kuroto Dan & Obtaining OOO's Power
In 2018, Kuroto Dan, the head of the Dan Foundation, established his own country, dubbing himself 'King Kuroto Dan', after accepting a deal from Uhr in 2010 to become Another OOO. After Geiz goes to investigate and gets his hands on the Gemn Ridewatch (Kuroto's old rider form) in 2016, Sougo decides to go a different route and becomes the head of Kuroto's army.

Later on, Sougo met Eiji Hino, the past Kamen Rider OOO (erased because of Another OOO), who had become a politician and was imprisoned by Kuroto. Eiji gave Sougo the OOO Ridewatch, with Sougo becoming Zi-O OOOArmour to defeat Kuroto.

Time Paradox & Obtaining Gaim’s Power
While Sougo was facing Another Gaim in 2013 to save Geiz, he suddenly found the Gaim Ridewatch from nowhere and became Zi-O Gaim Armor, with a bit of difficulty. Eventually, Another Gaim was defeated, but suddenly, a mysterious entity pulled Sougo to an alternate dimension, eventually revealed to be Kouta Kazuraba (the old Gaim) as the Man of The Beginning. He asked whether it was right to depend on his own power to save his friend, before sending Sougo back to 2018.

Going Limbo & Obtaining Decade’s Power
After defeating Another Gaim and saving Geiz from the Helheim Forest, Sougo went into the city to stop Another Ghost, who was sucking people's souls away. However, when he attempted to defeat him, Tsukasa Kadoya, the destroyer of worlds working with the Time Jackers, stopped him and nearly made him lose his soul to Another Ghost. However, Takeru Tenkuji, the original Kamen Rider Ghost, was able to stop his soul being sucked away, leaving his soul displaced from his body and invisible to everyone but Takeru as he had the Ghost Ridewatch.

Geiz, realizing what had happened, went back to 2015 to fight Another Ghost, but just before he could be destroyed, Tsukasa interveined and stopped him again, giving him the Decade Ridewatch after neutralizing the Ghost Ridewatch. Sougo's soul was soon reunited with his body, and he became Zi-O DecadeArmor before regaining the Ghost Ridewatch, defeating Another Ghost while Tsukasa made his leave.

Be The One
"I am Kamen Rider Zi-O. The demonic king with the powers of all Kamen Riders, or so I'm told."

- Zi-O introducing himself to Sento Kiryu. At some point in his history, Kamen Rider Zi-O joined a battlefield where the first 18 Heisei Riders were engaged in battle against their numerous adversaries. This event was also witnessed by Sento Kiryu, Kamen Rider Build, which was inadvertently transported to this location as a result of experiments with the White Pandora Panel he conducted at some point following his battle with Kamen Rider Blood.

Arriving in his Time Mazine, Zi-O disembarked and found Sento, who noted the name "Kamen Rider" on his mask. Revealing to Sento that he possessed the power of Build, Zi-O used the Build Ridewatch to assume BuildArmor as he entered the fray. After striking several monsters with his Drill Crusher Crusher, Zi-O quickly performed a Vortex Time Break which wiped out all the Riders' opponents while catching the prior Riders in the crossfire. Reverting to his default form, Zi-O was left with Sento, who questioned who the Rider was and how he had his power. Introducing himself as Kamen Rider Zi-O, Sougo proclaimed himself as the demonic king with the powers of all Kamen Riders, while acknowledging that he was going by the word of others.

Personality
Sougo is described as an ambitious young man who desires to be a king. He had a hobby of learning the history of existing kings, even the Kings that are classified as Tyrants (i.e. Nobunaga Oda). However, upon learning of his alternate future self-being a tyrant, he decides to change his fate. The reason for his desire is due to a recurring dream he had since his childhood, where a man in black says he is a fledgling king and he has a mission to become so and protect this world.

Despite his grand ambitions, Sougo is a peaceful and genuinely kind man at heart, and will gladly take physical harm if it means stopping a conflict, much to Tsukuyomi’s confusion. He also took his duty as Kamen Rider seriously, as he fully understands the responsibility of his power to protect people, something he believes what a benevolent King would do. After being transported to 2068 and finally meeting Oma Zi-O, Sougo becomes terrified and appalled to the fact that Oma Zi-O "is" indeed him. As a result, he decides to allow Geiz to destroy his Ziku Driver to prevent Oma Zi-O from existing, and even goes as far to give up his dream of becoming a king. However, he comes back to fight after Geiz promises to stop him from going the path of evil and reminds him of his promise to become a good demon king.

Sougo seems to have a verbal tic by adding "Feels like it" (気がする) at the end of most of his sentences, mostly due to his optimistic approaches. Sougo also generally friendly and remains trustful to everyone, to the point that Sougo gives Geiz permission to use the Wizard Ridewatch to defeat Another Wizard in 2012.

Sougo exhibits fanatical admiration when in the presence of a regal figure (i.e.: Kuroto Dan). However, he also exhibits respect for ordinary people that have benevolent king-like quality (i.e.: Eiji Hino). This stems from the belief that he could learn from those individuals who have succeeded in their ascension and also understand what is needed for one to be a Benevolent Ruler. Resulting in him become one step closer to accomplish his own ambition. This character trait gives him intense focus, which extends to his combat prowess. In the ensuing confrontation with Geiz, Sougo displayed formidable combat skill and effortlessly defeated him, who is supposedly a trained resistance soldier.

Sougo seems to be a little more aggressive when he begins fighting. Sougo usually kicks Rider Armors to make them attach to himself, unlike Geiz who let the Armors attach to the user automatically.

Skills

 * Vast Historical Knowledge: According to Tsukuyomi, Sougo excels in history.
 * Keen Manipulator:  Sougo has a talent for understanding how people would behave and subsequently exploiting people around him to do his bidding like how he tricked both Geiz and Tsukuyomi into watching Another Wizard's magic show with him and how he took advantage of Woz to make him cooperate with him and Geiz. Geiz considered his manipulative capabilities to be a serious threat and an indicator of his potential to become an demon king.
 * Time Manipulation: Upon acquiring the Zi-O II Ridewatch, Sougo reversed time, allowing him to undo Geiz's defeat. This was done in civilian form, implying that the Ridewatch bestowed the power on Sougo directly.

Weaknesses

 * Poor Academic Performance: According to Tsukuyomi, Sougo is helpless in science and curricular subjects in school. This indicated when he first used the BuildArmor, and instead of proper equations, it simply listed sentences stating that he 'didn't know' or 'something I learned in grade school'.

Forms
Kamen Rider Zi-O transforms by inserting the Zi-O Ridewatch into the right-hand side of the Ziku-Driver and spinning the Driver 360 degrees. He accesses Rider Armor (ライダーアーマー) forms based on previous Heisei Kamen Riders by inserting Ridewatches into the left-hand side of the Ziku-Driver.

Zi-O can execute a finishing attack known as the Time Break (タイムブレイク) by pressing the Ride-On Starter on their Rider Ridewatch and rotating the Ziku-Driver. Time Breaks performed in a Rider Armor are named after the respective Rider's finishing attacks with "Time Break" after it.

Devices

 * Ziku-Driver - Transformation device
 * Ridewatches - Transformation trinkets
 * Ridewatch Holder - A strap to carry Ridewatches

Weapons
Handheld weapons:
 * Zikan Girade - Zi-O's personal weapon and Zi-O II's secondary weapon
 * Ride HeiSaber - Zi-O's personal weapon while using DecadeArmor
 * Saikyo Girade - Zi-O II's personal weapon

Suit-equipped weapons:
 * Drill Crusher Crusher - BuildArmor's personal weapon based on the Drill Crusher
 * Gashacon Breaker Breakers - Ex-AidArmor's personal weapons based on the Gashacon Breaker Hammer Mode
 * Booster Module - FourzeArmor's personal weapons based on the Rocket Module
 * Tora Claw Z - OOOArmor's personal weapon based on the Tora Claws
 * Daidaimaru Z - GaimArmor's personal weapons based on Orange Arms' Daidaimaru
 * Kamen Ride: Decade Card - In Ganbarizing, when Zi-O DecadeArmor and his Final Form Time utilizes Attack Time Break, he throws the Kamen Ride: Decade Card to his target and performs a variant of Decade's Dimension Kick.

Vehicles

 * Ride Striker
 * Time Mazine

Relationships

 * Tsukuyomi: Tsukuyomi is the one that first informs Sougo about his future as Oma Zi-O. Initially believed Sougo as evil as the future Demon King, Tsukuyomi joins Geiz at watching Sougo's every moves. Eventually, as Sougo shows his kindly disposition, Tsukuyomi mellowed and became his most trusted ally... until he evolved into Zi-O II, and she reaffirms that Sougo must be killed before ascending into Oma Zi-O.
 * Geiz Myoukouin/Kamen Rider Geiz: Geiz strongly believes Sougo is Oma Zi-O and is absolutely determined to kill him before he could become the demon king to prevent the future where Sougo supposedly becomes the tyrant that rules all with an iron fist. He refuses to call Sougo by his real name and cruelly refers to him as Oma Zi-O. At many points in the show, Geiz shows Sougo hostility, but over the course of the story, he begins to realize that Sougo isn't as bad as he once thought. When Sougo finds himself in the future, Geiz even outright begs Sougo to give up the Ziku-Driver to prevent himself from becoming Oma Zi-O, showcasing that his resolve to kill him has lessened greatly, and perhaps even sees him as a friend.
 * (Black) Woz: With Woz having seen his future master's history and dreams to become king, Sougo is often baffled each time Woz appears aside from delivering his speech of passing Rider powers onto him by his predecessors. Despite even when Woz briefly sided with the Time Jackers to "correct" him, Sougo doesn't even seem to mind. Nevertheless, Woz remains a loyal servant and messenger towards Sougo.
 * Junichiro Tokiwa: Sougo's uncle. Junichiro always wanted Sougo to face reality and take tests into university, but he still respect Sougo's dream to become king.
 * Future Sougo: His future self as Oma Zi-O. When Sougo first learned of him through Tsukuyomi, he initially didn't believe her. When he does believe her claim, he becomes determined to change his fate, but he otherwise still remains skeptic of how dangerous Oma Zi-O is according to her and Geiz. It wasn't until a proper meeting when he was sent to the future that he understood the reason why he was feared. Sougo despises what his future self has become, and is even more determined to change his fate.

Past Kamen Riders:

 * Sento Kiryu/Kamen Rider Build: The first senior rider Sougo met, Sento entrusted his past self to Sougo. They then fights together against the machination of Super Timejacker Tid.
 * Emu Hojo/Kamen Rider Ex-Aid:
 * Takumi Inui/Kamen Rider Faiz:
 * Kuroto Dan/Kamen Rider Genm/Another OOO: Sougo serves Kuroto to complete his ambition of becoming king but soon betrays him. Because he believe that a king must care about people (which Kuroto does not). Sougo also thinks he is the only king the world needs.
 * Eiji Hino/Kamen Rider OOO: Sougo likes Eiji's view about helping people that are reaching out to him, and notes that Eiji has a kingly disposition too.
 * Kouta Kazuraba/Kamen Rider Gaim: Sougo meet the version of Kouta that has been ascended into Man of the Beginning, and Kouta teaches Sougo the most important thing to have as a king: a person he can fully trust.
 * Takeru Tenkuji/Kamen Rider Ghost: As Takeru is the only one that can see Sougo in his spirit form, Sougo trusted him to enact his plan at saving Another Ghost's host. Then, Takeru helps Sougo return to his body.
 * Tsukasa Kadoya/Kamen Rider Decade: Tsukasa sees Sougo as a weakling, thus he provoked Sougo that he will destroy his world. Tsukasa also sends Sougo into the year 2068 to witness his rule as Oma Zi-O. After being cornered by Zi-O and Geiz however, he escaped with the promise to fight him again in a foreseeable future.
 * Shinji Kido/Kamen Rider Ryuki:

Others

 * White Woz: Being Woz from a different timeline where his future self was dethroned, the other Woz sees Sougo as a threat due to the fact that White Woz's loyalty lies with Geiz Revive. White Woz, however, doesn't see Sougo as a big hindrance.

Future Kamen Riders:

 * Rentaro Kagura: He met Sougo in a dream and helped him choose his own future and resist Sworz.
 * Mondo Douan: Sougo defended and saved him from Geiz, but later it turned out that the power of Quiz is needed for the Ridewatches.

Portrayal
Sougo Tokiwa is portrayed by So Okuno (奥野 壮). As Kamen Rider Zi-O, his suit actor is Seiji Takaiwa (高岩 成二).

Rider No.
As the leading rider protagonist of Kamen Rider Zi-O, Zi-O is labelled Kamen Rider #35 (仮面ライダー35号) and Heisei Rider #20 (平成ライダー20号).

Etymology
Sougo Tokiwa's name is play on, the place where Shotaro Ishinomori lived and started his manga career during 1956 to 1961. "Tokiwa" also carries the word Toki (とき), which can be translated into time when it is written in kanji "時".

"Zi" in Zi-O's name could mean either time (時) or character (字), representing his "watch" and "Katakana" motifs while the "O" means king (王). It may also be for the number 20 (2 - Ji, 0 - Ō), referencing that Zi-O is the 20th Heisei Rider.