Kamen Rider: I Became Dark Decade

Protagonist and villain + the ultimate fun-seeker + invincibly despicable Gu Yu transmigrated to the Kamen Rider world and became the Dark Decade. From then on, he began his career as a villain. An evil scientist who released the Gurongi, a servant of the Black God, an associate of Shirou Kanzaki, vice president of Smart Brain, an executive at Foundation X...