When she is 16 in the spring, Takemiya Naho gets a peculiar yet detailed letter from her future self, ten years ahead. Initially, she assumes it is a joke, but the events described in the letter actually come true, including the arrival of a new transfer student who sits beside her in class, Naruse Kakeru. The letter mirrors her diary entries exactly, even down to the same characters. It is only two weeks later, when Kakeru returns to school, that Naho finishes reading the letter...