Mashiro is a delinquent with bad grades and an even worse attitude. During summer vacation, his mother hires Gaku, a college student with decent grades and average looks, as a part-time tutor. To motivate his student, Gaku offers some unconventional rewards for each problem Mashiro solves. Yet soon enough, summer comes to an end and the two part ways, each returning to their normal lives. Several years later, Mashiro has moved to Tokyo for work, excited to start life as a real adult. But when he arrives at his accommodations, who should be waiting for him but his former tutor and one-time crush, Gaku!