Kosei Arima is the protagonist of the anime series "Shigatsu wa Kimi no Uso" (Your Lie in April). He is a piano prodigy who loses the ability to hear the sound of his own playing after the death of his abusive mother. Kosei becomes detached from music and life in general, until he meets Kaori Miyazono, a free-spirited violinist who inspires him to return to music. Throughout the series, Kosei undergoes significant personal growth as he navigates his complex emotions and relationships, ultimately rediscovering the joy of music and life.