"The truth is, I have memories of the future." ―says a mysterious girl who appears before the third-year high schooler Aruto Mozumi. Having lost his childhood memories and the ability to hear the piano, Aruto can only watch as his younger brother Tokio shines with natural genius. Why does the sound of the piano escape him? Weighed down by this vague unease, he cannot even bring himself to confess his feelings to the classmate he likes. It is now his final summer of high school. Aruto's fate begins to shift when he is guided by a girl who holds memories of the future. The curtain rises on a fleeting, bittersweet love story of one unforgettable summer.