Second-year student Naho Takamiya thinks it's a joke when she receives a letter from her 26-year-old self, forewarning the tragic future of a boy named Kakeru. But the advice proves true when he transfers to her school-just like the letter predicted. As their lives intertwine, Kakeru's dark past keeps him from opening up to anyone, and every day becomes a challenge for Naho to change his future. Fortunately, she isn't all alone in her task. Surrounded by a close group of friends, there may be more hope than Naho expected. Will their combined efforts be enough to prevent the greatest regret of their lives?