Monster or human... What sleeps deep in the darkness? The Leviathan, an enormous spaceship, drifts in spaces, abandoned in a galaxy far, far away. When looters break into the abandoned ship, they discover the diary of a middle-schooler, Kazuma, who documented the horrific fate of its passengers. Shocked, the looters read on, but as they do, they reach a chilling realization-there is still one survivor somewhere inside! Along with the looters, the reader will piece together the decades-old tale of an innocent school trip to Earth with a tragic and brutal ending, as sudden explosions destroy the hull of the Leviathan. Trapped in space without enough oxygen left to wait for rescue, Kazuma documents the mental collapse and treachery of his teacher and classmates as they realize that the only hope for survival is the cryopreservation unit at the heart of the ship... which can only fit one person. A bloody battle for survival ensues as friend turns against friend, teacher against student, and each survivor is forced to confront the value of their own life.