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) 

Rising pop star Mima has quit singing to pursue a career as an actress and model, but her fans aren’t ready to see her go... Encouraged by her managers, Mima takes on a recurring role on a popular TV show, when suddenly her handlers and collaborators begin turning up murdered. Harboring feelings of guilt and haunted by visions of her former self, Mima’s reality and fantasy meld into a frenzied paranoia. As her stalker closes in, in person and online, the threat he poses is more real than even Mima knows, in this iconic psychological thriller that has frequently been hailed as one of the most important animated films of all time. 
 
(Source: Shout! Factory) 
 
Note: The film received an early premiere at the Fantasia Film Festival on August 5, 1997.

Mary Elizabeth McGlynn is an American voice actress, ADR director and singer-songwriter best known for her involvement in music production in multiple games from the Silent Hill series, and her extensive English-language dubbing of various anime, animated films and video games.

Shiho Niiyama was affiliated with Aoni Production. Niiyama was famous for voicing Kō Seiya, otherwise known as Sailor Star Fighter, in Sailor Stars and Deedlit from Record of Lodoss War among other character roles (see below). She was also involved in one seiyū group, Virgo, who are the voice actresses of the anime and game, Ojōsama Sōsamō. She was diagnosed with leukemia in 1998, and died of internal bleeding following pneumonia in 2000. She was 29 years old. After her death, her ongoing roles went to Tarako, Satsuki Yukino, Makiko Ōmoto and Junko Noda. Niiyama's last work was the voice of Deedlit in Record of Lodoss War.

Veronika Neugebauer was a German voice actress and actress. Apart from a few anime roles she was well-known as the voice of Neve Campbell in the Scream series and Gaby Glockner in TKKG. A few years ago she also did voice over work for MTV Germany.