It’s the spring of Naho’s second year in high school, and Naho receives a letter from herself, 10 years in the future. The letter accurately depicts what’s about to happen, including details on a transfer student from Tokyo, Kakeru Naruse, who ends up sitting beside her in class. On top of that, the letter also begs Naho not to invite Kakeru out with her group of friends on that day alone, but why?

Kakeru enters the soccer club as a provisional member, just as the letter says. When the topic of lunches comes up after practice, Kakeru jokingly asks Naho to make lunch for him as well. Naho finds herself bewildered by his words, but feels pushed to act by the letter from herself 10 years in the future, which tells Naho that she wishes she had made lunch for Kakeru.

Naho is so concerned about Kakeru’s date with Ueda-senpai over the holidays, she can’t help but seem preoccupied and unable to focus on her friends’ conversations. Ever since Kakeru started dating Ueda-senpai, Naho has found it difficult to have a proper conversation with him. Naho regrets not directly telling Kakeru how she really felt the day Ueda-senpai asked him out, but what will she do now?

It's the last day of the school festival. Naho and Kakeru have promised to watch the fireworks together. However, just before they start, Ueda-sama gets in Naho's way. Will Naho get to experience watching the fireworks with Kakeru like her future self did?

The letter from the future details the regret felt by everyone for being unable to celebrate Kakeru's birthday. As such, high school Naho and the gang pester Kakeru about what he wants until the big day. On the other hand, 26 year-old Naho and the gang gather at the late Kakeru's grandmother's house to celebrate his birthday, like they had promised in the past.

Naho feels relieved now that she has the support of all her friends. On top of that, Kakeru and Naho begin to get even closer. Finally, the day of the athletic festival comes. What do Naho and the gang do to insure Kakeru can enjoy the festival from the bottom of his heart?