After meeting the peculiar expert Izuko Gaen, Koyomi Araragi, a third-year high school student, finds himself exiting an unknown void. Despite feeling uneasy, he is comforted by the presence of his girlfriend Hitagi Senjougahara. Together, they navigate the puzzling landscape to make sense of Araragi's past and present. However, their lives are upended by Ougi Oshino, a new transfer student whose proposal shatters Araragi's very foundation. As he investigates a supernatural phenomenon, Araragi uncovers a truth that was best left hidden.