Makoto, Kousuke, and Chiaki are three inseparable friends who are about to get out of school for the summer. On one unlucky day, Makoto trips and falls on a strange walnut-shaped object. On her way home, she finds that the brakes on her bike have failed, sending her right into the path of an oncoming train. But just before the moment of impact, she wakes up to see that it’s suddenly a few seconds before her impending doom. Eventually, Makoto realizes that she has somehow gained the ability to travel through time to the past. This opens up a new world of possibilities and opportunities for her, blissfully unaware of the consequences it has on the people around her.