She's a student at Setouchi Keijo Training School, and a member of the Elite Class in said school, where she ranked first place in the entrance exam. She's an infighter, and has a pretty wide range of special techniques at her disposal. She's also most likely lesbian, as she's often seen flirting with the other girls, as well as the fact that several of her specials have the intent of pleasuring her opponent, she also states at one point that she rather has cute girls than hot guys. Upon graduating from Setouchi, Mio officially becomes a B-Rank Keijo player. Sometime later, she is able to advance to the A-Rank.