Bewitching woman's play, aching memories of forbidden pleasure

Megumi's divorce from her husband has been accepted, and she moves into the house where her aunt Tsuyako and her daughter Itsuki live. Tsuyako is happy to be back again after a long time, but Itsuki's expression is cloudy. That night, Itsuki has a hard time falling asleep and listens quietly in front of Tsuyako's room. Then, as expected, I could hear the joyous voices of my mother and Megumi soaking in the joy of being reunited. The next day, Itsuki questions Megumi about her relationship with her mother. In fact, Itsuki also had a relationship with Megumi in the past...