When the burdens of adulthood and the harsh reality of corporate bullying betray one's childhood dreams, many would wish to return to their innocent youth to relive their lives and make the right choices. Stunned by the proposal presented to him, 27-year-old Arata Kaizaki hopes to turn his life around through a once-in-a-lifetime opportunity. On his way home from his part-time job, Arata is persuaded by Ryou Yoake, an employee of the ReLife Research Institute, to participate in an experiment designed to help him overcome his difficulties and re-enter the corporate world. As part of the ReLife experiment, Arata's physique is reverted to that of a 17-year-old, and all he must do is relive his high school life for one year. Waiting for him at the end of the experiment is a job offer that he has been struggling to secure ever since leaving his first company. With few other options, he decides to go along with this plan. However, possessing adult-like tendencies and having many years since his last formal education, Arata steps into an unexpectedly challenging territory—a normal day of high school.