Meet Kadokura Kyouko, grade school teacher, 33 years old, single. She has a gentle and caring personality and loves her job. Unfortunately she is only popular with her pupils, so her prospects of ever getting married seem... grim.
And Yamato Kazuki, university student, 20 years old, future goals: marrying Kyouko-sensei, becoming an astronaut(?). He's been in love with Kyouko-sensei ever since she became his homeroom teacher in 4th grade. Now finally an adult and having enough money to buy a ring, he decides to propose to her and she—in some way or other—agrees to become his girlfriend.
But even though theoretically a couple now, their teacher-student relationship doesn't seem to have changed much. What will become of this unlikely pair?