Also known as Riderman, the fourth the Kamen Rider, Jyoji Yuuki worked as a scientist for Destron until one of its agents frames him to have him branded as a traitor. To punish Yuuki, he is dipped into acid, causing him to lose his right arm, but manages to escape.

To clear his name, he vows to defeat Kamen Rider V3, taking on the name of Riderman. He later finds out the truth behind Destron from V3, and decides to join the fight against the evil Destron.