Hirose Ayato, the main character who lost his mother several years ago and now lives with his father.
One day, his father decided to go on a long business trip overseas for two months including the summer break. This meant that Ayato would be spending the entire period by himself.
Ayato's father was worried about the situation and consulted with a friend he knew in the neighborhood, a married woman by the name of Ninomiya Rinko. She recommended that he contact a "housekeeping agency" she knew of and he decided to request it for his son.
However, this wasn't your average housekeeping service - it was a "mama" agency where a registered woman would come as a "mama" and take care of housework and daily life for an agreed-upon period of time.
Starting with Rinko, who actually works for the company and openly comes as Ayato's "mama".
She is joined by Kiyoko, a married woman who has known Ayato for a long time and also wants to be Ayato's "mama".
Additionally, Kana—the president of the mama agency service and newly married staff member Tsumugi join the fight as well.
A rich and strange mother-child life begins.