Kamen Rider 4

Kamen Rider 4 is a web series which was released as an accompanying special to the film Super Hero Taisen GP: Kamen Rider 3. It introduced a new rider, Kamen Rider 4, who is the fourth Kamen Rider cyborg created by Shocker after Kamen Riders 1, 2, and 3. The plot goes around a time loop created by the Shocker that resets whenever someone dies, but whenever the loop resets Shocker itself somehow grows stronger and stronger. Thus, it is up to the Riders to decide whether to keep on fighting a useless battle... Or end the loops for good by sacrificing one of their own.