Kotaro Sato is a 5-year boy that moves in an apartment building that usually doesn't allow children. Kotaro introduces himself to his next door neighbour, Karino Shin, who is intrigued and wonders what could be the circumstances that could have led to this puzzling situation. Kotaro also meets his other neighbour living on the same floor, Akitomo Mizuki, who seems to be experiencing some challenges with the person she's dating. (Source: Annie at MyDramalist)