Flea Mutant (4) - A flea monster. It has great jumping abilities. Flea Mutant was used by Professor Kuromatsu to inject his subjects with some chemical followed up with a steroid Kuromatsu used. Hayami was his first subject for him to be a fast racer, but it ended up turning him into a werewolf-like monster later on. Gorgom used the "Coward Hormone" to have Flea Mutant inject it into Kotaro. Once Kamen Rider BLACK killed Flea Mutant with his Rider Kick, Hayami returned to normal.