Riko Akutsu

Akutsu is Ooyama's classmate and their seats are next to each other in class. She is a gyaru and is referred as a "delinquent" by Ooyama. She uses his room as a hang-out spot, and drops by almost every day after school. She likes cat, and Ooyama once found on her phone a video of her trying to befriend one while making cute sounds like "nyaan"