Ouka Asahi is a supporting character in Onii-chan wa Oshimai! She is Mahiro Oyama's classmate and a cheerful, friendly girl who helps create a lively school atmosphere. Ouka is often seen interacting with Mahiro and the other students, contributing to the series’ slice-of-life comedy and school-life setting. She represents one of the ordinary classmates around Mahiro, adding warmth and normalcy to the story while highlighting the contrast between everyday school life and Mahiro’s unusual situation.