Have you read Yuusei no Fool? It's another manga from Kure Yuki. It's about Sena, a girl who (un)fortunately having a twin sister who'll become a queen. She's being a substitute for her sick twin sister and enter a training school.
Mm, I think Sena (and her twin sister, Nina) looks a lot like Kaho. There's black hair Len who cann't play piano and there's Fudou Yosuke. Oh! I almost forgot to tell, there's princess Azuma too!