A short introduction where 26-year-old Naho Takamiya and her fellow friends are planning to write letters to their 16-year older counterparts.
Naho begins her tale by discussing how she is unhappy with every moment of her life and decides to write her counterparts in her 16th year about the mishaps she has suffered.
Ten years ago, Naho woke up late and received a letter that was written by the adult version of herself.
She read the first paragraph of the letter while at school and is sure that she’s actually tardy. The letter also states that a student who is transferring will be sitting beside her.
It occurred. Kakeru Naruse introduces himself and is seated alongside Naho. After the class has finished sooner, Naho and her friends take a stroll to meet and become friends with Kakeru.
Later, Naho read the letter over and again and is struck by the similarities in her writing as well as the content of her diary as well as the letter.
In the days following, Naho observes the absence of Kakeru. In Kakeru’s PE course, she reads the letter saying that she would not be able to play softball and will eventually cause her to regret the decision.
Kakeru returns to the class. Kakeru speaks to Naho about joining a sports club and the foot that she injured because of its size.
In the softball match, Naho’s teammates invite her to play, and she is initially hesitant. However, due to the letter and some encouragement from Kakeru she gets up and plays the ball player for their game of softball.
Naho strikes the ball, and it goes homerun. She wins the game. They also become champions as Suwa as well is the winner of the football match.
Naho is now convinced that the content of the letter is authentic and real after she has read the following pages and discovers that Kakeru will pass away. The letter requests Naho to look at Kakeru.