She's been Touya's childhood friend since way back—a year ahead of him in school. Her family owns and runs a ryokan in the Yumoto district, so she's basically tied to the hot springs business. As for her and Touya, there's clearly something there on his end; he's got feelings for her but he's way too shy to actually say it outright.
Content compiled by AnimeList.moe from publicly available sources.
