No Longer Human is told in the form of notebooks left behind by the principal character, Ōba Yōzō (大庭葉蔵). There are three notebooks chronicling Ōba's life from his early childhood to his late twenties. The notebooks are bookended by a preface and an epilogue by a nameless narrator, who is given Ōba's notebooks by a mutual acquaintance ten years after they had been written.