Touko Ozawa wakes up inside an unfamiliar ship. Her memory is hazy, and there is a needle mark on her arm. There, she encounters two young people, Chisato Kanagi and Hitomi Mikami. What they have in common is that they have no memory of how they got there. Inside a ship echoing with the sounds of inhuman footsteps and the eerie cries of "Gitagido Detade Rabba...", who exactly took them and for what purpose—? In search of answers, the youths begin their exploration.