Hi! I read a shoujo series sometime ago about a girl who moves out to the country, and her crush becomes her stepbrother (or is it the other way around - that she develops a crush on her stepbrother...? I can't remember).

It later turns out that the stepbrother is in love with with their slightly overweight teacher, whom he has known since he was younger, and the girl eventually winds up with the stepbrother's friend instead. (Although her own friend briefly dated said stepbrother's friend for a while.)

The teacher also played piano or something like it, because I remember some dramatic scene in which the gang goes to watch her performance.

I can for the life of me not remember the name of the series - could anyone please help me?

Principal?
sounds kind of like it...I haven't read it in a while but the teacher thing kind of matches up with and maybe the step siblings thing? Sorry if it's not the one but there are a lot of mangas where the crush becomes stepsiblings