Parents Send Their Daughter To Work For A Nice Old Man, Unaware He's A Psycho

The movie begins with Taeko, her husband Shamoto, and his daughter Mitsuko attempting a silent family dinner. Mitsuko's defiance and a shoplifting incident lead them to Murata, a charismatic tropical fish store owner who offers Mitsuko a job and impresses the family with his luxurious store and friendly demeanor despite an underlying tension between Mitsuko and Taeko.

Murata proposes a business partnership to Shamoto, which Taeko eagerly accepts after Murata has an inappropriate encounter with her. Shamoto is hesitant but eventually agrees. During a meeting, Murata poisons his business partner Yoshida, revealing his violent nature and forcing Shamoto to help dispose of the body, threatening his family if he resists.

A terrified Shamoto is forced to burn Yoshida's bones and dispose of his flesh with Murata and his wife, Aiko. Murata confides in Shamoto about his traumatic past. A detective later approaches Shamoto, revealing Murata's history of disappearances, leaving Shamoto increasingly trapped and horrified by the monster he's allied with.

Yoshida's family, including a Yakuza brother, confronts Murata, who, with Shamoto's rehearsed help, manages to evade suspicion. Tsutsui, Murata's legal consultant, and Aiko are secretly having an affair, and Tsutsui attempts to recruit Shamoto to help kill Murata. Murata discovers the affair, poisons Tsutsui, and forces Shamoto to participate in disposing of Tsutsui and his driver's bodies, further solidifying Shamoto's unwilling apprenticeship in murder.

Murata, pleased with Shamoto's involvement, offers Aiko to him as a reward. An enraged Shamoto attacks Murata, learning that Murata had also slept with Taeko. In a violent struggle, Shamoto stabs Murata and Aiko. Aiko, in a twisted act, finishes off Murata.

Shamoto, now feeling empowered, declares himself the 'new Murata' and kisses Aiko. He then violently confronts and drags Mitsuko home. At home, he assaults Mitsuko to prevent her from leaving and then confronts Taeko about her affair, assaulting her as well. He leaves both unconscious and calls the detective, informing him of Aiko dismembering Murata's body.

Shamoto returns to the cabin and is attacked by Aiko, but he eventually stabs her to death. When the detectives arrive with Taeko and Mitsuko, Shamoto shockingly stabs Taeko to death. He then attacks Mitsuko, proclaiming that 'life is pain,' and slits his own throat. Mitsuko, in a final bizarre act, rejoices over her father's death, kicking his corpse.