Kyouta Kuremoto is a high school student who loves his 3-year-old sister. His parents both work, and they also do the housework and take care of the children. Sumi Akiyama is a lonely girl with beauty and a clear mind. She distanced herself from everyone because of her aura. One day, Kyouta, who was attending the entrance ceremony at his sister's kindergarten, surprised to find Sumi taking pictures like a cameraman. "Iku, how cute..." It turns out she loves her little brother! Knowing that they take care of their younger siblings, they gradually begin to deepen their relationship. Cooking, picking up their siblings at kindergarten, weekend dates. Yes, the relationship between the two is exactly like "mom friends." A childcare romcom has begun!