Rie Nozaki

Rie is a first year student. She is Shoko's accompanist for the concours.

It was she who warned Kahoko about the fact that her accompanist Manami Mori had hurt her arm before the start of the Fourth Selection.

In the credits of the anime she is named 'Akira Nimi' (新钆 晶).

Source: Wikipedia, own experience.