One day, the protagonist, “Takumi” witnessed it…
His mother “Mayumi”, and his friend “Eita” together, engaged in carnal pleasure.
Fleeing from the sight of this, he runs into his friend’s mother “Ayako”, and together their relationship evolves into one between a man and a woman.
The two butt heads, and so they challenge one another,
And so begins the mother-son group sex competition…