Ouka Nakiri is a supporting character in TONIKAWA: Over The Moon For You. She was a middle school classmate of Nasa Yuzaki and is the same age as him. Her family runs a hardware store, and she later runs an electronics store of her own. She has straight black hair tied in a ponytail, is fairly tall, and tends to wear comfortable clothing.

Ouka has a bright, tomboyish personality and a brisk, no-nonsense manner that gives her a refreshingly straightforward presence. She thinks logically and sharply, and she tends to view situations from a slightly unusual angle. She is practical and capable, especially when it comes to tools and electronic equipment, which suits her work running an electronics store. She does not appear to have any strong desire for romantic relationships and seems content with her independent, business-oriented life.

In the story, Ouka is reintroduced when Nasa and his wife Tsukasa visit her store because they need tools to install their air conditioner. Tsukasa is surprised to learn that Nasa's old middle school friend is a young woman. Ouka helps the couple with what they need, and her interaction with them reflects the easy, familiar rapport of an old friendship. Her connection to Nasa is rooted in their shared past as classmates, and she serves as a reminder of that earlier period of his life.

Ouka's role in the series is minor but meaningful. She gives practical support to the main characters and demonstrates a self-sufficient, level-headed approach to life. Her development is limited compared to the central cast, but she is consistently shown as reliable, straightforward, and skilled with her hands and with technology, with notable abilities in handling tools and electronics as part of her everyday work.