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...