Naho Takamiya's first day of her sophomore year of high school is off to an uneasy start. After waking up late, she receives a strange letter addressed to her. However, the letter is from herself—10 years in the future! At first, Naho is skeptical of the note; yet, after witnessing several events described to take place, she realizes the letter really is from her 26-year-old self. The note details that Naho's future life is filled with regrets, and she hopes that her younger self can correct the mistakes that were made in the past. The letter also warns her to keep a close eye on the new transfer student, Kakeru Naruse. Naho must be especially careful in making decisions involving him, as Kakeru is not around in the future. With the letter as her guide, Naho now has the power to protect Kakeru before she comes to regret it once more. One morning, Naho Takamiya receives a letter in the mail claiming to be from herself 10 years in the future. The letter reveals a series of events that are supposed to take place that day. At first, Naho thinks it's just a prank; but when the letter mentions a transfer student named Kakeru Naruse, who really ends up transferring into her class later that day, she is forced to believe in its contents. As Naho continues to read the letter, her future self mentions several regrets, urging Naho to take the right decisions now. Somehow these regrets all seem to be connected to Kakeru, and with the burden of the knowledge that the boy wouldn't be with her and her friends in the future, will Naho be able to make the perfect choices that will alter what seems to be fate?