The story focuses on a cold and distant 17-year-old girl, Nanaka Kirisato, who only cares about studying to get good grades in school and being accepted into a good college. Nenji, her childhood friend, doesn't really care about school and will often get into fights. Soon, Nanaka has an accident that causes her mind and memories to be reverted back to the time when she was 6 years old. Nenji ends up becoming the 6-year-old Nanaka's babysitter until they can find a way to turn her back into the 17-year-old Nanaka, which causes trouble and comedic situations.