OVA
Description
Sawa Kannagi, heir of the family tasked for generations with guarding the hidden Mermaid Hill repository holding a preserved mermaid corpse and its research archive, alone knew its location. This pivotal legacy defined her actions. She is the identical twin sister of Towa. When Towa contracted a terminal illness, Sawa attempted to save her by administering mermaid blood obtained from the repository, driven by sisterly devotion and her own desire to test the substance for potential immortality. The experiment failed catastrophically: Towa survived but suffered permanent deformities, including a monstrously transformed right arm and stark white hair. Their father concealed Towa by falsifying her death and imprisoning her in a basement cell for decades. Sawa complied with this arrangement.
While Towa remained imprisoned, Sawa pursued a conventional life, marrying, bearing a child, and maintaining outward normalcy while keeping her sister's existence secret. After their father's death, Sawa released Towa, and the twins coexisted in the family home, their relationship strained by bitterness and unresolved resentment. Towa repeatedly demanded the location of Mermaid Hill, a secret Sawa steadfastly refused to disclose.
Sawa became complicit in Towa's medical torment. As Towa's deformed arm caused chronic agony, Sawa facilitated Doctor Shiina's macabre surgeries, grafting limbs from deceased young women onto Towa—a cycle repeated every few years as each transplanted arm deformed. When the immortal girl Mana was brought to their home after a fatal accident, Sawa participated in the plan to harvest her arm. After Mana unexpectedly revived, Sawa initially supported her sister's schemes but later shifted allegiance, freeing the captive Yuta and confessing her guilt over Towa's condition, motivated by a desire to protect Mana.
The climax occurred at Mermaid Hill, where Towa forced Sawa to reveal its location. There, Towa exposed Sawa's original selfish motivation: using Towa as a test subject to gauge the mermaid blood's effects before potentially consuming it herself. In revenge, Towa attempted to force-feed Sawa mermaid flesh to inflict identical suffering. This plan was thwarted when Sawa collapsed and died of cardiac arrest, leaving Towa's vengeance unfulfilled. In accordance with Towa's final wishes, Sawa's body was cremated alongside her sister's during the burning of the Kannagi estate.
While Towa remained imprisoned, Sawa pursued a conventional life, marrying, bearing a child, and maintaining outward normalcy while keeping her sister's existence secret. After their father's death, Sawa released Towa, and the twins coexisted in the family home, their relationship strained by bitterness and unresolved resentment. Towa repeatedly demanded the location of Mermaid Hill, a secret Sawa steadfastly refused to disclose.
Sawa became complicit in Towa's medical torment. As Towa's deformed arm caused chronic agony, Sawa facilitated Doctor Shiina's macabre surgeries, grafting limbs from deceased young women onto Towa—a cycle repeated every few years as each transplanted arm deformed. When the immortal girl Mana was brought to their home after a fatal accident, Sawa participated in the plan to harvest her arm. After Mana unexpectedly revived, Sawa initially supported her sister's schemes but later shifted allegiance, freeing the captive Yuta and confessing her guilt over Towa's condition, motivated by a desire to protect Mana.
The climax occurred at Mermaid Hill, where Towa forced Sawa to reveal its location. There, Towa exposed Sawa's original selfish motivation: using Towa as a test subject to gauge the mermaid blood's effects before potentially consuming it herself. In revenge, Towa attempted to force-feed Sawa mermaid flesh to inflict identical suffering. This plan was thwarted when Sawa collapsed and died of cardiac arrest, leaving Towa's vengeance unfulfilled. In accordance with Towa's final wishes, Sawa's body was cremated alongside her sister's during the burning of the Kannagi estate.