A high school teacher named Narumi Yohei, deeply devoted to researching marine pollution, works at Hinohama Fisheries High School. His laboratory regularly receives deformed fish and abnormal organisms collected from the sea. One day, an utterly bizarre, unidentified fish is brought in, unlike anything seen before. Its grotesque appearance captivates the researchers, though its identity remains a mystery.

That night, a female student who assists Narumi stays alone in the lab to examine the strange creature. As she draws close, the creature attacks her, releasing a viscous substance or tentacle-like appendage that envelops her. The next day, the creature has vanished. Soon after, the girl notices scaly patches emerging on her neck. The scales spread across her body, her skin hardens and discolors, and she begins secreting slime. Gills and other fish-like features appear, accompanied by intense pain and suffering.

Narumi secretly attempts to find a cure, but the transformation accelerates uncontrollably. The girl loses her human appearance and struggles with despair as her humanity slips away. Experimental treatments fail, and she ultimately perishes in the lab, fully transformed into a scaled, inhuman form. Narumi is left devastated, forced to confront the consequences of his research and the broader danger of marine pollution. The mysterious organism's origin remains unknown, and the tragedy is buried without resolution.

The story is a body horror narrative that blends environmental dread with visceral, grotesque transformation, emphasizing the irreversible cost of human negligence.