The protagonist, Yanamori Takahiro, is bathing his daughter when his mother-in-law, Ninose Yaeko, comes to help. The situation takes an unexpected turn, leading to a secret encounter between him and Yaeko. Later, they act as if nothing happened, and the family gathers for dinner. But it turns up that protagonist's sister-in-law, Ninose Nanami, seems to be up to some mischief under the table. Takahiro wonders what will happen next, as he was just visiting his wife's family to introduce their grandchild.