I Turned the Tables and Won Over the Beloved's Younger Brother

I haven’t decided on the title or the names of the male and female leads yet. I’ll add the blurb later.

A story about an almost-romantic interest going public, and a young woman turning around and flirting with their younger brother.

Sweet, proud young woman x tall, obedient, purehearted puppy-like guy

Theme: Be diligent and take things seriously.