Ryoma Sengoku

Ryoma Sengoku (戦極 凌馬) is the creator of the Sengoku Driver and the Genesis Driver. He works under Takatora Kureshima for their secret project. Ryoma Sengoku transforms 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 implants his brain into a powerful to temporarily assume the role of Hikaider (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 Overlord, which is the image that appears to be Deemushu existing in the ruins, without telling Takatora about the Inves' leader's existence.

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 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 being touched by Kaito's speed about strength and power, he personally invites Kaito to join his team.

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 & Overlord 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.

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 Overlords.

After analyzing the battle of the Overlords with Baron, Ryoma kicks Kaito off the team as he can no longer fight the Overlords 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 Overlords, Mitsuzane tells them that they can easily find the Overlords if they adhere to his plans.

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 Overlords make their first appearance to Yggdrasill, going on the offensive, destroying the campsite. Upon Takatora's realization of the Overlords, 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 offer them a task to stop him from getting the Forbidden Fruit.

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 to fight, proven when he easily defeated Kouta in Jimber Lemon Arms and Kaito in seconds with his sheer power.

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 distain for not knowing how Kouta got the Kachidoki Lockseed and immediately picks up the fact someone is helping Kouta, but doesn't know who.

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

Equipment

 * Genesis Driver - Transformation device
 * Arms Weapons:
 * Sonic Arrow - Duke Lemon Energy Arms' personal weapon
 * Lockseeds - Gives access to Duke's form changes, depending on which arm the lock is

Portrayal
Ryoma Sengoku is portrayed by Tsunenori Aoki (青木 玄徳), who previously portrayed Aguri Kusugami in Garo: Yami o Terasu Mono. His character in the 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, 9-30
 * Kamen Rider × Kamen Rider Gaim & Wizard: The Fateful Sengoku Movie Battle