The H-Man

On a rainy night on the outskirts of Tokyo, Misaki is killed while attempting a getaway. The police go to Misaki's apartment to investigate and question his girlfriend, Arai Chikako. Arai reveals that Misaki hasn't returned home for five days, deepening the mystery.

Arai is a cabaret singer who encounters Masada, a Jyoto University professor, at the cabaret. She gives him a note to deliver to Misaki, but the note is confiscated and Masada is taken into police custody. This early contact plants the seeds for Masada's later theories.

In the police briefing, Masada theorizes that Misaki's disappearance could be the result of his physical form melting away due to radiation exposure in the rain. The police dismiss this strange theory, but it introduces the idea of a liquid creature at the heart of the case.

That night, Nishiyama, a drug gang member, sneaks into Arai's apartment to threaten her and uncover Misaki's whereabouts. Arai can't provide the information, and Nishiyama escapes by the window, followed by gunshots; the police find a pile of clothes and a gun on the floor.

In the morning, Arai confirms witnessing a man dissolving, lending credibility to Masada's hypothesis. Masada and Dr. Maki prepare to present the fishermen's testimony at the medical institute, where a frog test underscores the radiation-disintegration effect.

The fishermen recount seeing crew members disintegrate into liquid forms, leaving only clothing behind, which aligns with Arai's testimony. This corroborates Masada's growing theory about a radiation-activated liquid creature.

With the new findings, Arai agrees to lead the police back to the cabaret. The police raid yields arrests, but Uchida escapes to Emi's room with the gang's stash.

During the raid, the H-Man appears and dissolves the waiter and Emi, and later Detective Sakata. The carnage heightens the urgency to stop the creature.

Inspector Tominaga and the others devise a plan to use a high voltage discharge to stop the H-Man’s infiltration by lighting Tokyo's sewer system on fire. The plan targets disrupting the creature's ability to move upstream.

Uchida kidnaps Arai and takes her into the sewers to retrieve the drugs stash. Masada finds a piece of Arai’s clothing floating in the water and rushes into the sewers to rescue her.

Uchida is killed by an H-Man, and Arai is rescued by Masada. They escape the sewer in time as flames burn all the H-Man, ending their reign of terror.