After a catastrophic accident at a secret military facility specializing in personality modification, a small group of survivors is left stranded on a quarantined island. As they wait for a rescue that never arrives, paranoia grows and tensions rise among the group. Under the guise of leadership, the mysterious Shiori Tadokoro begins to manipulate and torture the survivors, utilizing the remnants of the facility's dark research to exert sadistic control over them.
The survivors are devastated to discover they have been abandoned on the island, leading to a breakdown of order and escalating violence. As a mysterious entity known as Mayumi begins to manipulate the group, tensions peak in a brutal assault on Nanae and the sudden death of Mr. Matsui. Under Shiori's cold guidance, the cast descends further into a nightmare of psychological torture and hidden agendas.
As the Madam and Ikegami maintain their control over the island's inhabitants, a dark conspiracy involving personality transplants and the mysterious Organization comes to light. While Mio descends into fear and Runa's precious pendant is lost, the discovery of a dead body reveals the lethal stakes of the experiments being conducted in secret.
Hiroki's sadistic experiments with transplanted personalities reach a breaking point as he captures and torments Mio and Runa. Amidst the chaos and psychological manipulation, Kaoru decides to betray the organization to save the girls. After a violent confrontation that puts an end to Hiroki's research, Kaoru secures Mio and Runa's safety and leaves a poignant farewell letter, sacrificing her own future to ensure their rescue from the island.