Kōsei Arima

The protagonist of this work. A 3rd-year student at Sumitani Municipal Junior High School (14 years old). His birthday is March 28th. He is 165 centimeters tall. His favorite foods are egg sandwiches and Moo-Moo brand milk.

To fulfill his mother's dream of raising him to be a world-class pianist, he practiced diligently under strict guidance from a young age and won numerous competitions. However, due to his precise and flawless performances, he was often ridiculed with nicknames such as "Human Metronome," "Mother's Puppet," "Mechanical," "Competition-Only Pianist," "Sheet Music Servant," and "Competition Mode." At the age of 11, he performed with emotion in hopes of cheering up his mother, but was met with corporal punishment and scolding from her. Unable to contain his emotions, he told his mother, "I wish you would just die," which became their last conversation. Since then, the memories of his mother became a trauma, causing him to develop a condition where he couldn't hear the sound of the piano he played, leading him to distance himself from the piano. He had a significant impact on his peers, becoming quite famous in the classical music world. He was the reason Emi Igawa started playing the piano and was a role model for Takeshi Aiza.

One day in April, through his childhood friend Tsubaki Sawabe, he met the violinist Kaori Miyazono. Although their first impression was terrible, as she mistook him for a peeping tom, he was captivated by her unique performance at a competition. Despite being constantly swayed by the free-spirited Kaori, he gradually became attracted to her. After Kaori collapsed and was hospitalized before the gala concert, he felt frustrated by his inability to do anything and expressed his desire to play together again by having her listen to his performance at the Kurumigaoka Junior High School Festival (commonly known as "Kuru Festival"). However, when Kaori collapsed again before the East Japan Competition, he became fearful of playing the piano due to the fear of losing someone important and refused to practice with Hiroko Seto. Despite being in the worst mental condition, he participated in the East Japan Competition and received a standing ovation by playing "for the people who gave him music." After the competition, he received a confession in a letter from Kaori's parents.

He hopes to advance to Okutsu Music University High School, which is outside the prefecture.