Ryoma Sengoku

Ryoma Sengoku (戦極 凌馬) was the creator of the Sengoku Driver and the Genesis Driver. He worked under Takatora Kureshima for their secret project. In reality, he had secretly planned his own agenda behind Takatora's back until the time came to betray him. Ryoma Sengoku transformed into Kamen Rider Duke (仮面ライダーデューク) using the E.L.S. 01 Lemon Energy Lockseed with the Genesis Driver. He later temporarily implants his brain into the powerful android Hakaider (ハカイダー).

Past
During a development of the Sengoku Driver with Takatora. The first test failed until in the present, the prototype version has been completed. Prior to Takatora getting medical attention, Ryoma got a report from Yoko that the Inves' leader called an Over Lord, which is the image that appears to be Demushu existing in the ruins, without telling Takatora about the Inves' leader's existence due to Takatora's insistance of putting humanity first above themselves.

He was also involved in recording the fate of Yuya Sumii in Helheim and Kouta Kazuraba's first transformation as Gaim is unaware he was fighting his own friend.

Beat Riders Saga
Sometime after the events of Bravo defeating Gridon and Kurokage, Ryoma arranges a meeting about Oren's portfolio, a man with military training. Later, Ryoma talks to Takatora about the new model which he replies to Ryoma that he will test the belt for humanity's sake. After, being requested by Sid to have multiple Lockvehicles, Ryoma views this as an opportunity to have all 7 prototype Sengoku Drivers in the Helheim forest. However, seeing Takatora is not pleased to have street rats in the forest, Ryoma warns Takatora to not destroy his precious work. During the Inves breakout of this event as they run rampant to Zawame City, Ryoma aids Gaim through the use of the Yggdrasill's tower through the use of a cloaking mechanism and beam weaponry.

Yggdrasill Saga
Ryoma later has Takatora test the Genesis Driver, impressed with its output and stating that they're one step closer to understanding the Helheim forest. Ryoma is seen once more, transforming with the Lemon Energy Lockseed, watches Sigurd kill Ryoji Hase. In the aftermath of this event, he formally introduces himself to Kouta and Kaito, asking for their permission to continue using them in his quest for power. However, when the two escape, he finds himself puzzled when his equipment (the Lemon Energy Lockseed and the Genesis Core slot) is stolen. Though, initially confused on why someone would steal the incomplete core slot prototype, Ryoma uses the data fed back from Kouta's Sengoku Driver to improve the mass-production models. Realizing Mitsuzane's inner darkness, he covers his actions when he "betrays" Yggdrasill by aiding Kouta. When he views the readings of the data fed back from the fight between Jimber Lemon Gaim and Marika, Ryoma decides to test out his Genesis Driver on Kouta. While apologizing for his inability to restrain his power, he easily decimates Jimber Lemon Gaim and Baron without breaking a sweat. After canceling his transformation, he realizes that Yoko never used the Genesis Driver to it's maximum potential, wondering why she's holding back. After hearing about Kaito's speech about strength and power, he manipulates Kaito into searching for the Over Lords without giving him the necessary preparations to combat them.

When a Crack appears on a bridge in the middle of the city, he asks Takatora if they should resort to use the Scalar System, however Takatora wants to minimize damage as possible, sending Ryoma down to the other side of the Crack in the Helheim Forest. With a squad of Kurokage Troopers, Marika, and Gaim, he explains to Kouta about Project Ark and how humanity will be culled down to one-seventh in order to kill off the potential 6 billion Inves that might come into fruition in the next ten years. In addition to this revelation, he also tells Kouta that the Sengoku Driver will help the remainder of humanity as it converts Helheim's fruits into Lockseeds and enables the wearer to absorb the nutrients safely without side effects. As the Crack closes, Kouta steals Yoko's Peach Energy Lockseed and rushes to HQ to destroy the Scalar System.

Helheim & Over Lord Saga
Ryoma apologizes to Mitsuzane for revealing classified information to Kouta. Though Kouta ignores Mitsuzane's pleas to stop, Ryoma is in shock and anger when Kouta utilizes the Kachidoki Lockseed, a Lockseed not created by him. Realizing that someone is helping him from the shadows all this time, he tasks Mitsuzane to investigate Kouta to find out who is helping him. Takatora, along with the group are informed of creatures that were more than a threat to humanity than the Inves by Mitsuzane. Realizing that their chance for power is dwindling, Ryoma gives Sid another Cherry Energy Lockseed, hoping that Sid will kill Kouta this time.

"There must be some kind of forbidden fruit that will grant an ultimate power to those who obtained it."

- Ryoma's conversation with DJ Sagara about the theory on forbidden fruit.

When Sagara appears in Ryoma's office. Ryoma reveals that mythology of a greater power is really the forbidden fruit of the Helheim and that Helheim has been here since the beginning of civilization. However, before he can have a longer conversation with Sagara, Sagara disappears telling them to find the Over Lords.

After analyzing the battle of the Over Lords with Baron, Ryoma kicks Kaito off the team as he can no longer fight the Over Lords with just his Sengoku Driver. However, Yoko requests for another chance for Kaito, giving him a Genesis Driver replacement. When figuring out how to find the Over Lords, Mitsuzane tells them that they can easily find the Over Lords if they adhere to his plans.

"You didn't understand me."

- Ryoma Sengoku's words before shooting down Takatora in Zangetsu Shin with the Sonic Arrow.

Reminiscing about the Sengoku Driver's origin, he is reminded of the day when he starts a separate path rather than work together with Takatora. When Takatora enters the room, Ryoma explains to him that there is no possible way to get more than a billion Sengoku Drivers. As the alarm sounds off, the Over Lords make their first appearance to Yggdrasill, going on the offensive, destroying the campsite. Upon Takatora's realization of the Over Lords, Ryoma decides to dispose of Takatora while he still has the chance. Transforming into New Generation Rider Duke, Ryoma defeats Takatora and has Sid slash him down and throw him off a cliff. While in the headquarters and erasing all records of Takatora Kureshima, he finds Sid destroying the equipment around the tree, causing the Headquarter's Crack to disappear and close. Later, he informs Kouta, Kaito, and Mitsuzane about Sid's betrayal as he offers them a task to stop him from getting the Forbidden Fruit. With the Over Lord's attack in Zawame City, Duke activates the Master Intelligence System, cutting off all communication devices in the city except for his own platoon that are engaging Demushu. When Demushu escaped after being overpowered by Baron and Knuckle, the Helheim's plants started to invade Yggdrasill Tower. Duke abandoned Marika and Yggdrasill as he leaves the rest to her.

Forbidden Fruit Saga
Ryoma later shows up in a holographic conference with Yggdrasill's executives of their international branches from London, Hong Kong and France. When the Executives threaten to arrest him after an investigation of what the Japan branch did to cause this disaster, Ryoma activates a bug in the executives' phones which sends information to the world about Project Ark's culling of the population, causing everyone worldwide to panic.

Returning to Zawame, he witnessed the battle between the Kureshima brothers, until Kouta shows up only to find Takatora's destroyed Sengoku Driver and Melon Lockseed. He later follows Kouta to Team Gaim's garage and mocks him about what happened to Takatora. Angering Kouta, Ryoma battles him until he is ambushed by Knuckle and Baron, as he cancels his transformation and is taken under the alliance's custody. Ryoma then reveals to the group that they can enter the tower by a secret pathway that he had used to escape Zawame City, before leaving the garage.

After leaving Zawame, Ryoma and Kouta are the only members able to infiltrate into Yggdrasill Tower while Oren alongside Hideyasu fought an army of Inves, Kaito alongside Yoko and Zack distracting Ryoma's turned off Suika Arms soldiers and Tulip Hoppers security. They are halted by Shinmugurun and Kouta fights it. Ryoma soon helps Kouta with the reasoning that it will be too bad for losing a needed test subject and also to show Kouta how to use the Genesis power in the right way. He proved himself to be even more superior than Kouta by defeating Shinmugurun very easily without a scratch. But, he decided to not finish him off and see how Kouta will continue it. He takes the data of Gaim Kiwami Arms when Kouta accesses it. After the battle is over, he makes a thought that it will be interesting to collect more data about Kouta's new power.

Once they reach the site where the kidnapped citizens are, Redyue appears to fight them, however Duke retreats while Gaim continues to fight the Over Lord. Later, Duke manages to reboot the Master Intelligence System, seeing that the Inves didn't invade his property as he checks the records prior to the Inves invasion. Once he heard Rosyuo's name while analyzing the footage, he thinks that the Over Lord is currently having the Forbidden Fruit in his possession. Once he found where Mai is, the possession of the Forbidden Fruit, and the Over Lords' leader to the the remaining Armored Rider resistances as Kouta and Kaito left, Ryoma also follows Kouta and Kaito in cloaking mode, in order to gather a data from Rosyou's power in Helheim. When the Forbidden Fruit from Rosyou becomes expired into nothingness and Mai went back to Earth, Ryoma also heard there's another Forbidden Fruit that Rosyou's hidden and discovered Rosyou had planted Mai the Forbidden Fruit in her. Ryoma returns to Zawame to take Mai to the hospital, along with Peko, Chucky, and Mitsuzane. Once they reach to the hospital, he examine her body as Ryoma believes that she might lose her humanity to become an Over Lord as this would shock Mitsuzane a lot. They then wonder about Rosyou's purpose of handing the Forbidden Fruit to Mai as Sagara appears to them that she will become the first women and reveals his true identity to them as Helheim himself. After Sagara explains his purpose to them and disappears, Ryoma inform Mitsuzane that he can remove the fruit from Mai, but believing that Kouta would interfere. Ryoma would give Mitsuzane the Yomotsuheguri Lockseed and warns him the consequence of using it before he leaves. Dissecting Mai to obtain the Golden Fruit, he disables Mitsuzane's Genesis Driver before promptly strangling him. However, the Golden Fruit manifests into an apparition of Mai and leaves the area. Ryoma is then encountered by Kaito and Yoko and disables their Genesis Drivers before defeating Baron Banana Arms. Ryoma falls to his death over the edges of a building when he is defeated by Kaito Kumon's Over Lord form - "Lord Baron".

Personality
Ryoma was one of Takatora's subordinates, and his and Sid's closest friend, a brilliant scientist in the Yggdrasill Corporation's research division who conducts experiments on the Lockseeds and is the inventor of the Sengoku Drivers and the Genesis Driver.

He is amoral in terms of using people as test subjects and expresses no interest in the Inves-based infections as his company's plan is his main focus. Despite his status as a scientist, he is dangerous in a fight, proven when he easily defeated Kouta in Jimber Lemon Arms (who managed to put up a good fight against the other New Generation Riders at the time) and Kaito in seconds with his sheer power. However, he rarely transforms and fights by himself. As shown, he would let the Kurokage Troopers and Marika fight the Inves in the Helheim forest and let the aforementioned riders capture Demushu while he himself just watched from a saferoom and eventually runs off leaving Marika and the Kurokage Troopers to die.

When Kouta revealed his newly-gained Kachidoki Arms, Ryoma showed a bit of anger and jealousy that such a Lockseed was not his creation, displaying him as arrogant, yet as a scientist, Kachidoki Arms is an unknown factor, with the above showing disdain for not knowing how Kouta got the Kachidoki Lockseed and immediately picks up the fact someone is helping Kouta, but doesn't know who.

Super Hero Time
Kamen Rider Duke alongside various other New Generation/Armored Riders poses with the ToQgers in the Gaim/ Super Hero Time opening. He also clashes with ToQ 3gou at one point.

Arms
Like the Armored Riders and his fellow New Generation Riders, Kamen Rider Duke's forms are called Arms (アームズ).

Devices

 * Genesis Driver - Transformation device (taken by Yoko Minato to transform into Malika after Ryoma's death, replacing her own which he had disabled)
 * Lockseeds - Gives access to Duke's Arms changes, depending on which lock is used

Weapons

 * Arms Weapons - Weapons that come with the Arms:
 * Sonic Arrow - Duke Lemon Energy Arms' personal weapon
 * WizarSwordGun - Duke Wizard Arms' personal weapon

Portrayal
Ryoma Sengoku is portrayed by Tsunenori Aoki (青木 玄徳), who previously portrayed in . His character in that show also used a bow and arrow for weapons similar to his current character's Kamen Rider alter ego.

As Kamen Rider Duke, his suit actor is Kenji Tominaga (富永 研司) who was previously the suit actor for Kamen Rider Kuuga and Kamen Rider Bujin Gaim.

List of Appearances

 * Kamen Rider Gaim
 * 7, 9-33, 38-43
 * Kamen Rider × Kamen Rider Gaim & Wizard: The Fateful Sengoku Movie Battle
 * Kamen Rider Gaim: The Great Soccer Match! The Golden Fruit Cup!