|This article is about a/an kaijin in Kamen Rider Black.|
Fly Mutant was sent alongside Grand Mutant 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 was possessed by Fly Mutant. Yuki got away with the three Phantom Mutants. With help from Mokoto, Kohtaro 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. Kohtaro 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 Fly Mutant's own substance back onto himself. Kamen Rider Black then killed Fly Mutant with the Rider Kick.
It can fly and spew an acidic substance from its mouth.
- Phantom Mutants (42) - Another set of Phantom monsters who assist Fly Mutant. The Mutants revived are a Spider Mutant, Silkworm, Rhinoceros, Cactus, Longhorn Beetle, Coelacanth, Slug Moth, Mushroom, Red Salmon and Rat Mutant. Kohtaro encountered the spirits of Silkworm, Rhinoceros and Longhorn Beetle Mutant attacking a police station and transformed into Kamen Rider Black. Since they are spirits, Kamen Rider Black could not harm them. They disappeared when Yuki got away. The next day, the Phantom Mutants attacked and Shadow Moon warned the people of Tokyo to take their leave. With Mokoto's help, Kohtaro found Slug Moth and Rat Mutant attacking people near a store and managed to repel them. Confronting Yuki/Fly Mutant at a railroad station, the Phantom Beasts were unleashed. When Rat Mutant's ghost grabs Mokoto, Kohtaro tells him to use his psychic powers to free Yuki. Once Mokoto uses his psychic powers to expel Fly Mutant from Yuki, the Phantom Mutants disappeared.