Although college student Natsuki Haibara has already secured a stable future for himself, he frequently thinks back to his high school days. At the time, he was socially anxious and overweight, and his attempts at becoming outgoing fell completely flat. One evening, Natsuki prays to be able to redo his teenage years and finds out the next morning that he has traveled back in time before his high school debut!

Having one month before the entrance ceremony, Natsuki immediately uses this chance to get himself into shape. When the first day of high school finally arrives, he makes a good first impression and befriends familiar faces, including Hikari Hoshimiya, his high school crush. Natsuki quickly realizes that his feelings for Hoshimiya have not changed and makes going out with her his new goal.

While enjoying time with Hoshimiya and his other friends, Natsuki rekindles his love for basketball and even secures a part-time job at a local cafe. But with new friends come unfamiliar challenges, and Natsuki must overcome them if he wants to enjoy his adolescence to the fullest.