Kamen Rider ZX: Birth of the 10th! Kamen Riders All Together!! (1984)

Ryo Murasame is an aircraft pilot. One day he is taking his sister out on a ride along the Amazon when they are shot down by a UFO. They survive only to be captured by the Badan Empire. His sister is killed, while Ryo becomes the Combat Roid known as ZX. His memory is erased by the Badan Empire, and he works as their agent of evil. This does not last long; an accident occurs which causes Ryo to regain his memory and escape Badan. At the same time he meets kamen rider v3, riderman and super 1, at first ryo thinks they are his enemies but the riders make him realise that they are here to defeat badan empire and ryo joins with the veteran riders to defeat Badan empire