Favoring simplicity and avoiding trouble, Mahiru Shirota's life takes a whimsical turn when he picks up a stray cat named Kuro. This seemingly innocent act unravels a chain of events as he discovers that Kuro is no ordinary feline but a lazy vampire who transforms in sunlight. Reluctantly forming a contract with this unexpected guest, Mahiru is thrust into a perilous world of supernatural conflicts and bloodshed, challenging his belief in keeping things uncomplicated.