Kamen Rider Stronger: The Movie(1975)

Waniida from Black Satan attacks a young boy and long-time Kamen Rider ally Tōbei Tachibana, but Kamen Rider Stronger and Electro Wave Human Tackle run in to make the save. However, Shigeru and Yuriko fall into separate traps and are captured by Black Satan. Yuriko fights for her life as Shigeru is brainwashed by the organization.