Mie Toyooka, who moved to this town a year ago, was troubled by her son Hiroki's reclusiveness. He was often at home, even though he was well past the period where he could get used to his new surroundings.

At that time, Kumi Kouyama, who lived next door, invited him to join the "Mutual Aid Association". Mie decides to join for the sake of her son and for her own spare time.

However, the "Mutual Aid Association" is a front for its real name, "mama club".

Waiting for Mie were the boys. Waiting for Hiroki were the club members' mothers.

Boys of the same age as her son gathered together, in the classroom at night, at home,
they squirt out their immature semen to these older women....

[From official site]