Drive Saga: Kamen Rider Brain Season 1

Brain awakens and finds himself kidnapped by an evil organization named Mu, whose primary aim is global conquest. Chosen for his high IQ, his body was rebuilt and he was about to be brainwashed when the process is interrupted.

As Brain and Crystal Peppler are in hiding, Brain tries to transform but cannot. Peppler suggests that Brain was able to transform before because he was in grave danger.