Yukiko is a critically ill patient at Morita Hospital who requires a kidney transplant to survive. Her boyfriend, Tadashi Kitayama, visits regularly but grows emotionally distant after meeting Tomie, who uses the alias Reiko Mizutani. Tomie manipulates Yukiko by poisoning her with lies that Tadashi desires her death and is involved with "Reiko," worsening Yukiko's distress and contributing to her declining health. This emotional turmoil triggers a medical crisis, necessitating an emergency blood transfusion. After Tadashi murders Tomie under her manipulative influence, Tomie's kidney is designated for Yukiko due to a compatibility match. The hospital's chief doctor authorizes the transplant after Tomie's accomplice, Satoru Takagi, fraudulently identifies the deceased donor as his daughter "Hanako." The operation initially seems successful, with Yukiko showing recovery signs. However, Yukiko soon suffers severe abdominal pain and swelling. Examinations reveal the transplanted kidney mutating grotesquely, developing limbs and a human head identified as Tomie. Surgeons excise the growing entity, which emerges as a sentient Tomie head. Despite removal, residual Tomie cells retain a foothold within Yukiko's body. Post-surgery, Yukiko undergoes significant physical and psychological changes. Her personality shifts toward vanity, cruelty, and aggression, mirroring Tomie's traits, indicating a loss of her original identity as Tomie's cellular influence consumes her. Concurrently, a fully regenerated Tomie emerges from a separated head specimen stored in the hospital basement. This Tomie manipulates staff and orchestrates the destruction of other biological samples to prevent further cloning. After the basement is deliberately set ablaze, Tomie achieves full regeneration through Yukiko's compromised body, usurping Yukiko's existence. Yukiko's fate concludes with her complete mental and physical eradication by Tomie's parasitic biology.