Arisa lives with her husband and daughter's family of four. One day, she learns that her son-in-law, Youhei, harbors distrust towards her daughter. Concerned for their marriage, Arisa begins to investigate her daughter's personal life with Youhei. However, as they work together, Youhei becomes increasingly distracted by Arisa's voluptuous breasts. Gradually, he loses sight of their purpose, and his desires become uncontrollable in the presence of her lascivious bust.
