Anime: Akira
Manga: Akira
Kaori is entirely different in the manga to the anime (this is because the anime and manga are just about entirely different). In the anime, she's Tetsuo's girlfriend, and doesn't really do much (except nearly get raped). She really does appear to care for Tetsuo though, even after he goes a little crazy. Not much else can be said about her, since she rarely appears and gets zero real character development.
I can't really say much about her in the manga either, since she makes her first appearance in the fourth volume, and saying anything about her is a spoiler.Highlight the following text for spoilers. She joins the Tokyo Great Empire (run by Akira and Tetsuo), and is found taking food for her sick father. Sent with two other girls to have sex with Tetsuo, she is the only survivor, and basically becomes Akira's babysitter.Once again she doesn't seem to be a character with much development (okay, I've only read up to volume 4 and therefore I may be wrong; expect this description to be updated if I am), as is the fate of most lesser characters.