Sera's older brother, an antique shop owner, brings home a clockwork doll named Satsuki. Sera's kiss awakens Satsuki from his long slumber. Satsuki's constant smiles initially perplex Sera, but she finds herself increasingly charmed by him. However, Sera discovers a peculiar condition: when Satsuki cries, screws fall out with his tears. She learns that if the last screw falls, Satsuki will transform into an inanimate doll, never to awaken again.