Ruri

She is Zen's older brother's eldest daughter, when she was a child her mother and little brother died from starvation after an epidemic and a bad harvest, at that time her father was already dead too but it was never specified the cause, the most likely in a war somewhere, since then she was raised alone by Yuba, she's equally close to everyone in the village with the exception of Sayo and Shin as they were the ones who spent more time with her in her childhood when they were learning spirit arts together from Yuba and that as fellow orphans they hung out a lot too.

(Source: Seirei Gensouki Wiki)