Sarina lives with her two sons, her older brother Hayato and her younger brother Takeshi. Her father is not in her single-mother household, but her sons love Sarina, who is bright and kind, and she has lived with the three of them. However, one full moon night, Sarina, who has a different atmosphere than usual, attacks Takeshi and commits. The next day, Takeshi consults with Hayato, but he doesn't believe her. And then the night of the full moon comes again...
