7 needed to calculate an average
Daikichi's grandfather dies, leaving behind a young daughter named Rin. However, as most of the family is embarrassed at the idea of a 79-year-old man having a six-year-old child, they can't seem to figure out what to do with her. Disgusted by this behavior, Daikichi decides to take care of her himself, but he's a bachelor, has no idea how to raise a child, and doesn't even like kids! Now, Daikichi must do the normal things a parent does such as enroll her in school, buy her clothing and teach her about the life and world around her. But more importantly, he must also help her deal with her father's death and decide whether or not she should try to find her mother. Together, the two begin their unlikely relationship as father and daughter.
Each of these mangas is about a young adult suddenly being asked to look after a child who is not their own. The adult is reluctant at first, but grows more attached to the child as they spend more time together. The children also become quite attached to, and dependant on, their new caretakers.
Both of these series involve a young adult, living on their own, who has to look after someone else's child. (The main character in Gakuen Babysitters has to look after other people's children, as well as his own kid brother.)