Ryuichi and Kotaro are brothers who lost their parents in a plane crash. They are taken in by the chairman of Morinomiya Academy, who lost her son and daughter-in-law in the same accident, under one condition: Ryuichi must babysit the kids in the school's daycare room! This room was established to assist teachers with children, but it suffers from a staff shortage until Ryuichi becomes the first member of the babysitter club created to address this issue.
