Five years ago, a horrific event unfolded on Kamioki Island, erasing Mari Wakatake's memory while claiming the lives of all inhabitants. Now a reluctant student at a secluded girls' school, Mari remains oblivious to the vigilant surveillance aimed at her, anticipating the return of her lost memories. Unbeknownst to her, a chilling revelation lingers in her subconscious – she might not have been the sole survivor. As an enigmatic figure infiltrates Kaihou Academy, Mari finds an unlikely ally in a mysterious girl whom she feels drawn to but struggles to trust.