When I Brought a Lost Girl Home, the Most Beautiful Girl in My Grade Came Out the Front Door

Ayano Shirakawa is the most beautiful girl at school, always neat and graceful. Yusei Kuroda has no connection with her other than being in the same class, until one day when he saves Ayano's younger sister from an accident, and his ordinary life is changed forever.

"Just tell me what you want me to do."

Shirakawa cheerfully and innocently offers Kuroda a reward for helping her sister. She cooks for him at her house, and then comes over to his place to clean his room, too. They visit a summer festival together, and as he feels like he's getting closer to Shirakawa, she acts more daring than usual, too... These two will get together sooner or later. This is a romantic comedy of the highest caliber.

(Source: Fantasia Bunko, translated)