She is a kitsune (fox spirit). Spirits of her kind feast on people's passions. Good spirits find people obsessed with a passion and take it away, helping them. And bad spirits stay with people and grow passions in them to eat it later.
Su is very young fox (with only one tail) so she is not sure if she is good or bad yet.
Her passion is gluttony so she is a great cook and loves to feed everyone :D

She is the youngest of three siblings, she has two elder brothers: Kim (a three-tailed fox) and Taiki (a nine-tailed fox).

She can turn into a fox or look like a normal human, but her mail form while she is in human world is this one.