Mysterious Girlfriend X: Ayuko Oka

Oka is 143 centimeters tall, but is very full-breasted. She was seen kissing Ueno by Tsubaki after school one day, but it didn't seem to bother her much. After she happened to see Urabe and Tsubaki together on their way back home, she tries to become friends with Urabe despite the latter's initial rejection, and with her devious insight and intelligence, she starts helping Urabe develop and deepen her relationship with Tsubaki. She becomes the first friend of the unsocial and very reserved Urabe.

OVA