Shinobu Katsuragi

Shinobu Katsuragi is the secondary antagonist in the final arc of Kamen Rider Build and the current second-in-command of Faust. Shinobu was a former member of INSET, the husband of Kyoka Katsuragi and the father of Takumi Katsuragi. Originally believed to be dead, it was revealed that Shinobu was not only working with Evolt on the Lost Bottles, but also was the leading member of the Mars exploration group ten years ago, making Shinobu the one that is truly responsible for Evolt's actions and the subsquent Sky Wall Disaster. Shinobu was also in charge of examining Ryuga Banjo due to his extraterrestrial origins. He is later revealed to have his own Build Driver, which he uses to become another Kamen Rider Build.

He was portrayed by Joji Kokubo.

Ten Years Ago
Ten years prior, Shinobu was the leading member of the Mars exploration group. When Evolto-possessed Soichi Isurugi touched the Pandora Box and caused the Sky Wall Disaster, all three nations put the blame onto him. He faked his suicide, and (with the aid of Reika Kine), he smuggled himself out of Touto on the day he supposedly died.

After hiding inside his secret hideout, Shinobu continued to work with Evolt. He later created Lost Bottles, man-made Fullbottles that allows a human to transform into a Smash, although this made said human become more aggressive and easier to control and manipulate. The Lost Bottles would play a vital part in Evolt's endgame.

Revealed to be Alive
During the first initial years that Evolt was on Earth, Shinobu was tasked with repairing his Evol-Driver under Project Evol. However, the Driver was taken and hidden away by his son Takumi, where Sento would later find it and reluctantly return it to Evolto. After Sento and his friends discovered that Shinobu was still alive, they started to investigate about him. Unbeknowest to Sento, Shinobu was later resurfaced at a Faust hideout in Hokuto where he sided with Evolto while searching for the Lost Bottles.