It is the beginning of the summer season. Shuhei Amamiya is a fifth grader who moved to a rural town from Tokyo. Because he introduces himself to the class that his dream is to become a pianist, he quickly becomes the target of the class bully “Kimpira”, who tells Shuhei to go test his courage by playing a “broken piano” in a forest near the school. Rumor was that though the piano is broken, sound of the piano could mysteriously be heard at night. Shuhei is at a loss as to what to do with this sudden unreasonable demand, but is saved by his classmate Kai Ichinose, who says, “That piano still can be played!” Kai and Kimpira start a big fight, but they both run off with the shout from Ajino, the music teacher. Shuhei left behind alone, asks Ajino about the rumor of the “broken piano”. After school, Kai invites Shuhei to the “Piano Forest”. Deep in the forest, there is a grand piano with sunlight sifting down through the trees. Shuhei, who is studying the piano, tries to play it, but the piano makes no sound. For some reason, only Kai is able to play it. Kai says, “This piano is mine!” With shoes off and feet bare, Kai plays the piano in the forest wildly. The tone of Kai’s piano has a mysteriously attractive quality, and Shuhei is hugely moved by the sound that Kai brings out. Yet Kai says he “never learned how to play the piano.” For Shuhei, somebody like Kai is a shock. Shuhei has been giving up his playtime in order to practice the piano to become a pianist like his father, a world notable pianist. Shuhei invites Kai to his home and lets him play the piano, but Kai’s playing the regular piano was something unbearable to listen to. The next day, Shuhei tells Ajino how Kai can play the piano in the forest and how wonderful the sound is. Ajino enters the “Piano Forest” at night and encounters Kai playing the piano. The sound touches Ajino’s heartstrings. Ajino asks, “Why don’t we work on the piano together?” However, Kai feels that he is intruded and rages home. Kai visits Shuhei’s house again and listens to the piano. When Shuhei learns about the incident with Ajino, he tries to persuade Kai that “ This is your chance.” However, Kai displays no interest, and Shuhei is unable to say anything more. On his way home, Kai is unable to calm himself and stops by the school’s music room and encounters Ajino. Ajino plays the piano one song after another. Kai is forced to listen, but soon, his eyes begin to light up with excitement. Kai plays the songs he listened with the piano in the forest, and is able to play everything except Chopin. Not being able to play the song he wants to play grows to become a craving in Kai, and he begs to Ajino, “Teach me Chopin!!” Ajino sets one condition to Kai; he must enter a piano competition. Shuhei is also scheduled to participate in the same competition…. Kai with the talent of a genius, and hardworking Shuhei. The “passionate drama of friendship and struggle” over the piano between these two young boys will unfold on the silver screen.