Rei

Rei is a singer in the pop music group CHAM! After Mima left, Rei and Yukiko become more popular, which results of them getting into the best singing group charts. She does seem to care about Mima, even when she changed careers. In one scene in the film, Rei and Yukiko are on their radio talk show and when they bid goodbye to the audience, Mima's apparition appears. Although Rei is happy to see Mima, but is shocked when Mima suddenly leaves and goes after the apparition.

(Source: Satoshi Kon Wikia)