23-year-old school teacher Aoki Daisuke has a huge problem. One of his precocious 3rd grade students, Kokonoe Rin, has the hots for him! Indeed, the mischievous Rin has proclaimed herself to be Daisuke-sensei's girlfriend and is now on the warpath to win him over or get him fired... whichever comes first! And that is not the end of Daisuke's problems, though; he also has to find out what happened to Usa Mimi, a friend of Rin's who has yet to attend school.