Ryuga Banjo

Ryuga Banjou (万丈 龍我) is a 23-year-old ex-fighter who was wrongly imprisoned for the murder of a scientist named Takumi Katsuragi, who was involved with the Pandora Box. Abducted by Faust while in prison, Ryuga managed to escape with his humanity intact, which would lead him to join Sento Kiryu in uncovering the truth behind their shared experiences as Faust victims.

He uses the Cross-Z Dragon given to him by Sento to become Kamen Rider Cross-Z (仮面ライダークローズ), the secondary rider of Kamen Rider Build.

As war breaks out between Hokuto and Touto, Ryuga takes the Sclash Driver against Sento's objections to become Kamen Rider Cross-Z Charge (仮面ライダークローズチャージ) until it was destroyed when Ryuga protected the possessed Misora from Blood Stark's attack. However, the Dragon SclashJelly remains turned into Dragon Magma Fullbottle through unknown means.

Later, Using the completed Dragon Magma FullBottle and Cross-Z Magma Knuckle, He's able to Transform into Kamen Rider Cross-Z Magma (仮面ライダークローズマグマ)

In Episode 30, his humanity is called into question, implying Ryuga may not even be human, which is confirmed in the following episode, revealing he is of extraterrestrial origin.

Arrival on Earth
In 1994, 13 years before Sky Wall Incident, an unmanned space probe from Japan landed successfully on Mars and returned to Earth. After its return to the Nanba Heavy Industries Institute of Synthetic Science, the probe unexpectedly brought back an alien specimen in the form of glowing red slug-like creature, which made its way out of the probe and planted itself into Yuri Banjou, a security guard who was stationed there with her husband, through unknown means, causing her to fall unconscious while on duty. During a checkup at a hospital, she was discovered to be one month pregnant, which was the suspected reasoning behind her collapse.

A month later, Ryuga was born in Yokohama. To everyone's bewilderment, the child was in perfect health, weighing 3.2 kg despite his two-month gestation period. Because of this oddity, he was examined at a university hospital, discovering a cellular structure never before seen in humans in him. He was later be re-examined at the Namba Heavy Industries Institute of Synthetic Science, discovering his genes are of extraterrestrial origin. This resulted in periodic examinations from the Institute, under the supervision of Shinobu Katsuragi, until his parents' death.

Ryuga lost his parents in an accident at the age of 13. Ryuga doesn't remember the details of the accident or even his past experimentations, which he attributes to the trauma of the event. However, Sawa speculates that the researchers might have altered Ryuga's memories during the experimentation.

Present
As an adult, Ryuga became a professional fighter, eventually getting engaged to Kasumi Ogura. By the age of 22, Ryuga earned a lifelong ban from fighting for throwing a match; it is implied that he accepted a bribe in order to pay for the frail Kasumi's medical bills. To help his search for a new job, Kasumi directed Ryuga to Takumi Katsuragi, a researcher at the Touto Institute of Advanced Matter Physics, who was apparently looking for an assistant. However, when Ryuga came to Katsuragi's home to apply, he found the corpse of "Katsuragi" inside. Moments later, Touto's Guardians arrived and apprehended Ryuga. It would be revealed that it was Soichi Isurugi who called Ryuga the murderer, which would give Ryuga a ten-year sentence in prison.

While in prison, he was attacked by a prison guard working for Faust, who injected him with Nebula Gas. However, Ryuga's naturally high Hazard Level allowed him to escape mid-experiment with his memories and humanity intact. After fighting off the Faust scientists, he retreated to the sewers.

The Rabbit Tank Meets Dragon
Ryuga was eventually found by Touto's Guardians, who attempted to recapture him. Ryuga managed to fend off the Guardians and escaped before he was apprehended by Sento Kiryu, who had tracked him upon noticing his Smash-like energy readings. Upon realizing that Ryuga had undergone a similar experience, Sento began interrogating Ryuga in hopes of uncovering his past, despite Ryuga's frustrated belligerence. The two were interrupted by Strong Smash, who attacked Ryuga. However, Ryuga was saved by Sento, who transformed into Kamen Rider Build and defeated the Smash. Ryuga recognized the Smash's human identity as one of his fellow victims but was frustrated to find that the man had no memories of the experiments. The Touto government arrived soon after to retake Ryuga. Sento, believing in Ryuga's innocence, helped him escape.

Burn Smash incident
Sento brought Ryuga to the basement lab of the nascita café, where the former had been living for the last year. After meeting Sento's accomplices, Souichi and Misora Isurugi, Ryuga explained the circumstances that resulted in his arrest. However, the story was interrupted by Sawa Takigawa, a freelance journalist who had entered the base (due to Souichi and Sento's carelessness).

As a precaution, Ryuga was chained up in the lab, much to his chagrin. Misora took the time to explain the Fullbottle purification process to Ryuga, as well as Sento's job. Noticing Misora's smartphone, Ryuga goaded her into proving her ability to purify Smash energy. As planned, Misora left her smartphone where Ryuga could reach it, allowing him to contact Kasumi. However, much to his horror, Kasumi had been kidnapped by Faust as well. Given Kasumi's location by Night Rogue, Ryuga broke out of nascita and raced to save his fiancé. After another encounter with Guardians (which ended with being saved again by Build), Ryuga explained his motives to Sento but choked him into unconsciousness to prevent him from getting involved.

When Ryuga finally arrived at the location, he learned that he was too late: Kasumi had already been transformed into the Burn Smash. Unable to see his beloved hurt, Ryuga begged Sento not to attack her when the latter arrived. The two were quickly overwhelmed by the Smash and Night Rogue, upon which the latter revealed the horrifying truth: Kasumi's body was too weak, and removing her Smash element would be fatal. Realizing that Kasumi could not be saved, Ryuga begged to Build to end her suffering. Sento was able to separate Kasumi's consciousness long enough for her and Ryuga to say their goodbyes. Left almost broken by grief, Ryuga would have let himself be captured again if not for Sento, who reminded him that it would all be for nothing if he got arrested again. Kasumi's Smash essence was purified into the Dragon Fullbottle, which Sento gave to Ryuga as a memento of his beloved. Soon after, Sawa arrived, having discovered the identity of the guard who attacked Ryuga: Masahiro Nabeshima.

Continuing the Search
After some searching, Ryuga managed to contact Nabeshima. Nabeshima revealed that his family was being threatened by Faust, upon which Ryuga offered to smuggle them out of Seito to safety in exchange for Nabeshima testifying for his innocence (not realizing this was a trap set up by Night Rogue). With Sawa's help, Ryuga snuck to Seito. Upon retrieving Nabeshima's wife and daughter, Ryuga and Sawa were attacked by hijacked Guardians, barely escaping with their lives. Ryuga arrived in Touto to aid Build in taking down Nabeshima, who had been subjected to two Smash transformations by Faust. While Nabeshima was returned to his human form, the experiments wiped his memory clean, leaving him unable to recognize his daughter, let alone testify for Ryuga.

The next lead came in the form of Tatsuya Kishida, who was roommates (as well as bandmates) with Sento before the latter lost his memory.

Cross-Z charges up
In one fight, Ryuga was granted the Kuma and Televi Fullbottles by Grease as a concession when the Hokuto Three Crows interfered in their battle and breaking the rules. After giving the new pair to Sento, Ryuga was see that nascita finally had a customer in the form of Massugu Ubukata. Providing his customer with a canned coffee, Ryuga, foreseeing a boon in business, set out to acquire a bountiful stock of coffee beans, only to find the shop as vacant as usual when he returned.

Cross-Z Charges into Hell
Seito proposes a 3-on-3 representative battle to Touto. Ryuga is participating Round 2 against Fu Washio. Much to the surprise of Ryuga, the announcement depicts the name his opponent is "Hell Bro's", which he had never heard before. As Ryuga prepare his transformation, he is interrupted by the sudden appearance of the Gear Engine on Fu's hands. Fu uses it along with his personal Gear Remocon to transform into Hell Bro's, completely overwhelming Ryuga's expectations. However, Ryuga didn't waver and proceed to transform into Cross-Z Charge.

As Cross-Z Charge and Hell Bro's goes down on a fierce fight, Ryuga determination to not let Sento burden himself and end the war manage to overwhelm Hell Bro's. But, Fu suddenly claims that if he about to lose this proxy battle, Rai will be executed. Ryuga was torn between saving Touto or saving Rai as Fu take his chance to soundly defeat Ryuga. Fu later mock Ryuga by being too gullible as he fell to Fu trick, showing that Rai is in fact, never get captured Hostage. Although visibly frustrated, Ryuga accept his loss and exclaiming that Sento will be the one who end the war before leaving.

Ryuga predictions came out true as Build manage to defeat Rogue using TankTank form, and Ryuga celebrates Sento victory along with Misora, much to Kazumi ire.

Sclash Driver Destroyed, and Going Magma
"My power will overflow...my soul will burn...and my magma will surge!"

- Ryuga's exclamation upon becoming Cross-Z Magma After Vernage resurfaced from Misora's bracelet, Blood Stalk got his transformation knocked out after the queen blew a strong gust of wind at him. He then tried to attack her again, but Ryuga stood in the way. However, this resulted in Ryuga's Sclash Driver getting destroyed, and the Dragon Sclashjelly overheated to a burnt ball of ash.

Back in nascita, the Dragon Sclashjelly reacted to Ryuga's emotions, creating the Dragon Magma Fullbottle. Seeing this, Sento later made the Cross-Z Magma Knuckle for Ryuga to use with it as it was too dangerous for the Build Driver alone. This in turn, helped Ryuga fight off Blood Stalk and Hell Bro's with ease.

In the middle of dealing with Hell Bro's, Gentoku entered the scene, transformed into Rogue, fought, and sneakily explained what was actually Soichi's plan by whispering to them on every single strike he did. The truth was shocking for Ryuga as Rogue declared that he was not human and was the target for Stark not just by chance, especially on why Kasumi was kidnapped and killed. All of this was to give Ryuga his power and increase it over time.

After Sento knocked down Gentoku, he, Ryuga, and Kazumi went and found Soichi. As Soichi went serious, his strength proved to be far stronger than Build RabbitRabbit Form and had Kazumi knocked down unconscious. Ryuga asked Soichi if what Gentoku had told was the truth, shocking Soichi and claiming that it was true, making Ryuga mad but still unable to beat him.

As Soichi was about to kill Sento, Ryuga's anger became stronger which finally stabilized the Dragon Magma Fullbottle. Despite not being told about Cross-Z Magma Knuckle's ability to evolve his form, Ryuga used the Cross- Z Magma Knuckle and the Dragon Magma Fullbottle to transform into Cross-Z Magma. His new form was able to knock down Soichi and give him the chance to take Pandora Box as well as save the others.

Ryuga, the Humanity's End?
Ryuga was told by Soichi or Evolt that he was the same as him, the one who would destroy the world.

Personality
Ryuga is a hot-blooded and impulsive man, tending to lash out quickly. While nowhere near as intelligent as Sento, Ryuga prefers to confront problems directly using his fists and doesn't want to involve other people in his own problems. Also, unlike Sento, he does not overthink things, preferring to use common sense, as shown when he was easily able to guess two Best Matches on his own. He is shown to easily get startled, especially when the bell goes off indicating a Fullbottle is ready.

Beneath his tough exterior is an honest, selfless and honorable individual. It is implied that the cheating that banned him from fighting was to get money for his fiancée's medical treatments. Ryuga also has a friendly side, such as when he encourages Takehiko after Build removed the Smash essence from him.

Ryuga is also shown to have a selfless side, as when he attacked Blood Stalk out of anger for the sake of both Sento and Misora, completely disregarding the fact that Stalk framed him. He also directly apologize on Sento Behalf to the remaining Hokuto Three Crows, partially blaming himself due to letting Sento use Hazard Trigger for his own sake.

Upon constant usage of the Sclash Driver, Ryuga's personality becomes more aggressive with the single task of getting stronger and beating down his opponent. These side effects also remove his rationality to make decisions, but he is able to overcome these weaknesses with his strong will to save Sento from rampaging with the Hazard Trigger.

Ryuga appears to hold a lot of fondness for his childhood, as whenever he describes the circumstances of his birth, a bright smile is always on his face.

Powers and Abilities

 * Hand-to-Hand Combat: Ryuga is a skilled fighter, having fought professionally before getting a lifelong ban.
 * High Hazard Level: Initially, Ryuga's Hazard Level is above 2.0, allowing him to retain his humanity after exposure to Nebula Gas while still gaining physiological powers from it. According to Blood Stalk, while fighting, Ryuga can raise his Hazard Level, having raised it as far as 2.7. Originally, in a fight against the former, his Hazard Level was 3.0, which is high enough to use the Build Driver. Recently, however, his continued fighting as Cross-Z raised his Hazard Level to 4.0, enabling him to use the Sclash Driver. Ryuga's Hazard Level grows at a faster rate than any other Kamen Rider, to the point where his strength grows noticeably in a single fight.
 * Superhuman Strength: Ryuga has displayed enhanced strength: he was able to fight off numerous Guardians on his own, and break metal chains with his bare hands.
 * Smash Energy Signature: Since he is exposed to the Nebula Gas, Ryuga gives off an energy signature similar to a Smash, which alerted Sento to his location.
 * Altered Physiology: According to Sawa's speculation, Ryuga possesses a vast amount of alien DNA in his body. This allows him to utilize the Pandora Box's power like Stalk (albeit unintentionally) and absorb the same Power needed to complete Dragon Magma FullBottle. Furthermore, His eyes will glow red while doing so.
 * Fullbottle Augmentation: By using a Fullbottle in his hand without transforming, Ryuga can gain abilities based on said Fullbottle's traits:
 * Dragon: Ryuga's punches give off powerful shockwaves. Notably, his strong synchronization with the Dragon Fullbottle causes his power to increase with each use. Currently, it gets to the point where Ryuga is strong enough to even defeat a Hazard Smash while as a human.

Weakness

 * Short Temper: Despite being a capable fighter, Ryuga is shown to be easily provoked in most situations. When combined with the priority to prove his innocence, it sometimes caused a major sidetrack in Build's battles against Smash (such as transforming Tatsuya back into Press Smash just to locate Faust's base) without even forming the next phase of his plans.
 * Sclash Driver: (Previously) Although the Sclash Driver gives Banjou tremendous power, its usage slowly turns Banjou into a more aggressive person and yearning for power. Furthermore, the driver administers electrical shockwaves to the user after a period of time, canceling his transformation and rendering him unconscious. After learning from Sawa that Sento built a failsafe to destroy the Hazard Trigger and kill himself, Banjou overcomes his guilt and turns into Cross-Z Charge to stop Sento in his HawkGatling Hazard form. During the fight, the Sclash Driver begins to increase his aggressiveness, yet he manages to overcome it by reminding himself to save Sento, thus gaining control over his Cross-Z Charge form.

Devices

 * Build Driver - Cross-Z's transformation device.
 * Cross-Z Dragon - Slot adapter for Build Driver and personal familiar. After obtaining the Sclash Driver, it becomes the adapter for a Twin Breaker Finisher.
 * Cross-Z Magma Knuckle - Secondary slot adapter for Build Driver and secondary personal weapon.
 * Sclash Driver - Cross-Z Charge's transformation device (destroyed by Blood Stark with his Martian power)
 * Fullbottles - Cross-Z's Transformation trinkets.
 * Fullbottle Holder - Carrier strap for Cross-Z's Fullbottles
 * Dragon Sclashjelly - Cross-Z Charge's transformation trinket. Later, being overheated into a Dragon Magma Full Bottle.
 * Build Phone - Smartphone that transforms into the Machine Builder.

Weapons

 * Beat Closer - Cross-Z's personal sword.
 * Twin Breaker - Cross-Z Charge's personal wrist blaster.
 * Drill Crusher - Build's personal weapon borrowed by Ryuga.
 * Safeguard Rifle - Guardian's assault rifle, stolen by Ryuga on one occasion.

Vehicles

 * Machine Builder - Rider Machine shared with Kamen Rider Build.

Portrayal
Ryuga is portrayed by Eiji Akaso (赤楚 衛二), who previously portrayed Hiroki Nagase in Kamen Rider Amazons Season 2. As Kamen Rider Cross-Z, his suit actor is Eitoku (永徳), who returned in portraying "Secondary Riders" since Baron.

Etymology
The kanji used to spell his first name can poetically mean "I'm a Dragon" (竜我).