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?

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?

Naho can't give her Valentine's Day chocolate to Kakeru. Ever since what happened on New Year's Eve, Kakeru keeps putting distance between Naho and himself. But, through all the hardships, Naho refuses to give up and fully intends to tell Kakeru how she feels. And so, the time comes for everyone to face the fateful day outlined in the letters from the past, "Kakeru's Final Day."