S1·E14 Escape in the Rain

Sho awakens after his critical injuries from his confrontation with Enzyme II aka his father, Mr. Fukamachi. He apparently has no memories of rescuing him from Cronos, but when the group is attacked by Zoanoids, he finds himself inexplicably unable to transform. After they escape the Zoanoids, Sho is upset that he can't rescue his father if he can't change, and he is struck with a painful realization that he can't remember involving his father. Tetsuro surmises that killing his father has repressed both Sho's memories and his abilities to transform as a result.