Tamao is a quiet, introverted girl living with the Asakura family after being orphaned young—You's father, Mikihisa, took her in. She's got a pretty obvious crush on You, despite knowing full well that he's already engaged to Anna. Her shyness runs deep enough that she used to communicate through drawings in her sketchbook, pointing at pictures rather than speaking.
What sets her apart is her talent with divination via kokkuri board—basically the Japanese answer to a Ouija board. She's also an ascetic like Mikihisa, which means she's got her own pair of spirit companions: Conchi, a kitsune, and Ponchi, a tanuki. It's the same setup Mikihisa has, so there's a real connection between them in that respect.
Content compiled by AnimeList.moe from publicly available sources.