Suze and her childhood friend, Lulu, visit the renowned Bianca Aquarium. However, the latter ends up disappearing without a trace. Determined to find Lulu, Suzu wanders through the fearful aquarium. Suddenly, she is attacked by a mysterious woman who names herself "Retro" The aquarium director's wife, "Chris", lends Suze her hand in escaping the facility. The girl who's been continuously trapped within the aquarium, "Kitty". The only hint to escaping... is to become a creature of the aquarium. Suze must unravel the mysteries behind these women――― and discover the identity of the traitor...