Mayu Tobita

A young singer, about the same age as Sana herself. She appears only briefly in both the manga and the anime, but is often considered an important character regardless (she even appears in the intro of the second series of the anime, despite not even being in it). Tomita is a strict actress who takes her work very seriously, and is a bit stuck-up as a result. She regards Sana as a rival and finds Sana's laid-back attitude extremely irritating. It is also hinted that she likes Naozumi, so she gets easily jealous when he talks to Sana.

(Source: Wikipedia)