Hiroto Suwa spent his second year at a high school in Matsumoto beside Naho Takamiya and the transfer student Kakeru Naruse, and he put his own feelings for Naho aside for his friend's sake. This film revisits that year from Suwa's perspective, alongside the letters Naho received from her own future self asking her to watch over Kakeru. It retells and extends the television series rather than working as a starting point.