Yūko is a tall girl with messy and wavy chin-length black hair. She also has narrow green eyes.
In Trigger Mode, she, along with her teammates, wears a white body-fit armor over the top half of her body with purple gloves, a belt that wraps partially around her waist, and a shoulder strap exposed on her right side. This is connected to short black pants that then connect into long purple boots.
She is shown to be somewhat hot-headed, punching Jin when he gropes her. She is also shown to be quite persevering, battling with all her strength as she battled Murakami, who was far more skilled than her.
- "Yūko" (友子? which can also be read as "Tomoko") means "friendly child", while "Kumagai" (熊谷?) means "bear valley".
- Since she acts as Nasu-san’s guard a lot, her solo points aren't very high, but her blade handling and reversal techniques are quite considerable and even the male attackers acknowledge her superiority.
- According to Volume 11, she likes:
- meat udon
- all kinds of sports.