When Ayumi "Kouhai" Yurino learns that her senior Yuuki "Senpai" Hisamizu is heading to Minami High School, a fairly difficult institution to enroll in, she believes her current results are insufficient to pass the entrance exam. Despite this, Senpai gives her a word of encouragement and promises to tutor Kouhai if she succeeds.

One year passes, and Senpai finds Kouhai to be one of the new first-year students enrolling at his school. However, he also quickly realizes that his junior has become extremely flirtatious toward him! Now fulfilling his promise, the two experience many events together—whether they be funny, embarrassing, or even romantic.