Ryoma's Splinter Group is a team of Yggdrasill employees working with Ryoma Sengoku to overthrow the leader of Yggdrasil's research and development branch, Takatora Kureshima, and use the Helheim Forest situation to gain power for themselves.
Ryoma would later go on to recruit Kaito into his group. However, after seeing that his Sengoku Driver couldn't fare up to an Overlord, Ryoma considered letting him go until Yoko gives Kaito a Genesis Driver to allow him to have another chance
Seeing that Takatora has discovered the Overlords, Ryoma and Sid go to kill him. Takatora attempts to fight back, but gets defeated and knocked off a cliff.
Later, Sid betrays the group, destroying their crack lab and going to claim the Forbidden Fruit. However, he is quickly killed by Rosyuo.
During Demushu's attack on Zawame City, Ryoma flees, causing him to lose Yoko's respect and making her leave the group.