Guyver: Out of Control

Sho and Mizuki are walking alongside the river till Sho finds a rare artifact. When he touches it, numerous vines come out of it and he is sucked into the water together with the artifact, before Mizuki can react, she is surrounded by a bunch of monsters that call themselves Zoanoids. But suddenly, the guyver appears and defeats them all but because Sho has transformed into the guyver, Mizuki's life is in danger and he has to defeat Guyver II to save her.