Fly Mutant (42) - A fly monster. It can fly and spew an acidic substance from its mouth. Fly Mutant was sent alongside Baraom to find a psychic who can find the dead spirits in a plot to revive some of the defeated Gorgom Mutants to cause havoc in the city. They find one in a boy named Yuki and they trick him into assisting them. Fly Mutant then merges with Yuki's enegies to revive them as Phantom Mutants which causes a strain on Yuki's brother Mokoto. During his fight with the spirits of Silkworm Mutant, Rhinoceros Mutant, and Longhorn Beetle Mutant, Kamen Rider BLACK discovered that Yuki is possessed by Fly Mutant. Yuki got away with the three Phantom Mutants. With help from Mokoto, Kotaro found Yuki at a railroad station as Fly Mutant uses him to have the Phantom Mutants attack. After Mokoto drives Fly Mutant out of Yuki's body causing the Phantom Mutants to disappear, both of them collapse from the psychic strain they went through. Kotaro transforms into Kamen Rider BLACK and fights Fly Mutant. Upon being hit by the acidic substance, Kamen Rider BLACK summoned Road Sector who tackled Fly Mutant and then used its spray to send the substance back onto Fly Mutant. Kamen Rider BLACK then killed Fly Mutants with the Rider Kick.