Kotone's husband, Takashi, is away from home. At that time, Takashi's divorced older sister, Natsumi, temporarily moved into the house where Mr. and Mrs. Kotone lived. Since their parents have already passed away, Kotone and Natsumi have started living together. One night, Natsumi gets excited when she hears a gasping voice leaking from Kotone's room. The next day, the gaze of Natsumi looking at Kotone gradually changes mysteriously.
