Rui is a cute girl with short blue hair and bright red eyes. In most of the manga, she is often seen wearing her uniform, which consists of the standard white collar shirt, sweater vest, and a plaid skirt. After graduating high school, she is often seen in casual clothes or wearing a chef’s uniform for work, and occasionally she’ll wear pretty clothes on the monthly dates with Natsuo.
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.