Shiori is Iori's little sister. 3rd year in middle-school, Aries, blood type AB.
She lives in the countryside in the Kitahara family inn. Shiori hates the fact that Iori left home to go to college, because it means that she's next in-line to inherit the family inn. Neither Shiori nor Iori want to inherit it.

She appeared first in volume 7 and came with a purpose to retrieve Iori home and dump inheriting the inn onto him.