Sayonara Piano Sonata

The story revolves around a 16 years old boy called Nao, which is son of a music critic and has a hobby of fixing machines. On a visit to a junkyard he meets a girl which is supposed to be a piano prodigy, to their surprise, she transfers to his school and enters his life. On top of it, he has a strange senpai and his childhood friend who want him to join their band...

(Source: Sayonara Piano Sonata Wikia)