What would you do if you could leap backward through time? When 17 year old Makoto Konno gains this ability after an accident in her high school chemistry lab, she immediately sets about improving her grades and preventing personal mishaps. Before long however, she realizes that even innocuous changes can have terrible consequences. Changing the past is not as simple as it seems, and eventually Makoto will have to rely on her new powers to shape the future for herself and her friends.