Kamen Rider

A mysterious man appears in front of Supana after tracking him. He changes into a Malgam before attacking the former and Houtarou. Supana then transforms into Valvarad and counters, and so does Houtarou into Gotchard, but the Malgam escapes after Valvarad's counterattacks. However, the man, who is set on overthrowing Supana, kidnaps Rinne in front of Houtarou in order to lure his nemesis out. Who on earth is this man? And why is he so obsessed with Supana!?