Mermaid Forest

A truck strikes and kills Mana. Shiina, the old doctor who examines her, tells the police and Yuta that she survived and wandered away. Shiina takes her corpse to Sawa, an old woman, and Towa, a young woman with a heavily bandaged right arm. As he begins to replace Towa's arm with Mana's, Mana revives. Yuta realizes that Shiina lied and follows him to Sawa's and Towa's house, where local legend says a mermaid is buried. Towa has a Deformed dog kill Yuta. When he revives, Shiina, Sawa, and Towa confine Yuta to a cell in the basement. Towa kills Mana, to have Shiina transplant her head onto Mana's body. Sawa tells Yuta that she and Towa are identical twins. When they were young, Sawa had given Towa medicine made of mermaid blood to save her from a terminal illness, making her ageless, but Deforming her arm. Rather than admit his daughter was partially Deformed, their father had told everyone that Towa had died and had confined her to the cell in the basement until his death.