Sengoku X

Sengoku X, refered to as Professor Sengoku, was the creator of the Sengoku Driver and the Genesis Driver. He builded a Sengoku Driver as well and a Lemon Lockseed, which allows him to transform into Kamen Rider Sengoku.

Than he builded a Genesis Driver as well and a Lemon Energy Lockseed, which allows him to transformd into New Generation Rider Sengoku.

In one episode, He became part of Hakaider

He worked under Troy "Cage" Knight, his closest friend to stop Helheim's invasion. However, after a conversation gone awry with Troy, Ryoma secretly plans a coup against him. Sengoku X initially transformed as Kamen Rider Sengoku using a Sengoku Driver. He later upgrades himself along with Drew using the Genesis Driver and the Lemon Energy Lockseed in place of his regular Lemon Lockseed. Further upgrades were then given to Genesis Driver to allow him to combat the weaker Over Lords with relative ease as well with additional functionality.

Past
Like Taboo, he spent his childhood in the now-defunct Zawame Child Care Facility, where children with potential are experimented on and brutally raised to work for Yggdrasill in their future. Under Troy and Drew's father, he created his first products, the fully successful Forbidden Apple Lockseed (although it has a negative side-effect), and a negative life draining prototype Overlord Lockseed. He eventually was able to become a researcher for the company later in his life.

He met Troy "Cage" Knight at some point where they decided to work together to develop the Sengoku Drivers. He also the one who recruited Aaron and Emma to his side.

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

He was also involved in recording the fate of Yuya in Helheim and Dylan Lavigne's first transformation as Armor Warrior is unaware he was fighting his own friend.

Personality
Sengoku was one of Troy's subordinates, and his and Aaron'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 Dylan in Lemon Raiment Arms (who managed to put up a good fight against the other New Generation Riders at the time) and Baron in seconds with his sheer power.