The whole family spends incest with their mother at their parents' house where they left the nest.

Dai was born to the youngest of three siblings. To her mother, Maki, I got the impression that she was a child who couldn't take any effort... One spring of the year, the two brothers got a job and lived alone, and their father was on a single business trip, and their lives changed rapidly, and Dai and Maki began living together as a mother and child. Maki suddenly feels like she's lost her sense of loss when she suddenly becomes quiet... Seeing her mother's situation, Dai feels lonely and frustrated, and tries to regain her mother's love, which she has never been able to monopolise until now...