After escaping her abusive past, Seina moves into a Condominium where she notices a mysterious boy silently watching her from an abandoned building's Room every night. Strange things begin happening - people who hurt her disappear, and someone secretly protects her from danger. She soon meets Lucien, a cold and obsessive boy who has been watching her long before they met. As Seina gets closer to him, she discovers terrifying truths about his dark nature and must decide whether to run from him... or stay with the monster who loves her dangerously.