Kohaku Shiro

A very playful, older sister type... who's really, really small.
She's a dyed-in-the-wool country girl with an accent to match. However, she thinks she has no accent.

She can't see spirits and doesn’t understand magic in the slightest. Still, since she's the protagonist's honorary older sister, she's always on his side. She's a soothing presence in his life.

Lovebird spirits seem to really like her for some reason.