Shuichi Kagaya, a standout student and athlete, harbors a dark secret—he's no ordinary human. Transformed into a creature with monstrous strength, keen senses, and a profound loss of humanity, his world is forever changed. Bound by a girl named Claire who knows his truth, Shuichi grapples with his internal turmoil as he navigates his new existence. Claire, on her own quest to find her monster sister, lacks compassion for others. Despite clinging to his human values, Shuichi faces a bleak question: how long can he endure this precarious balance between humanity and monstrosity?