The plot of Piano no Mori revolves around Shuuhei Amamiya, a fresh transfer student, and Kai Ichinose, a young troublemaker hailing from the rough part of town. Upon his arrival at Moriwaki Elementary, Shuuhei boasts about his exceptional piano skills to his peers, only to become the target of bullies, headed by Daigaku Kanehira. Daigaku issues a challenge to Shuuhei, daring him to locate and perform on a cursed piano in the forest. This leads Shuuhei to Kai, who claims ownership of the instrument and is the only one capable of playing it. Fascinated by Kai's exceptional talent, Shuuhei accompanies him to the secluded location and delights in Kai's stunning rendition. Kai's mastery of the piano impresses not only Shuuhei but also the school's music teacher, Sousuke Ajino. As a result, Kai receives formal training to refine his talents.