Rui has short blue hair with bright red eyes. She has been seen wearing her school uniforms with a button white shirt with blue sweatshirt and a bow tie. With a red skirt and high socks brown shoes.
Rui is unwilling to talk to people not having friends. As her first meeting at a mixer to meeting new people. Thinking that it was boring there and willing to skip out of the mixer. And willing to have sex for the first time meeting not wanting to be treating like a kid due to some circumstances that will be mentioned later on.
Rui appears to be a very kind and loving girl through out the manga despite her cold and blank expression often shown. Although she acted cold towards Natsuo Fuji in the first couple of chapters, it is revealed Rui has feelings for her step-brother but is conflicted in being able to express them.