10-go Tanjo! Kamen Rider Zenin Shugo!!

Ryo Murasame was captured in the Amazon Jungle along with his sister Shizuka by the evil Badan Empire. Badan's agents murder Shizuka, then transform Ryo into an elite-agent of evil known as ZX. Initially Brainwashed and Crazy, Ryo miraculously regains his sanity and escapes Badan. He then encounters three strangers whom he initially assumes to be enemies. In reality, they are Riders V3, Super-1, and Riderman, who take him to meet the other Kamen Riders and welcome him to their fold. Afterwards, he joins them in battle, calling himself Kamen Rider ZX.