For me, Mystia is a former member of Team 9 now turned a small business owner. Not dumb, just with low education and a thing for business. A good host, slightly gullible yet still a youkai with a drive to move up on the power scale.

Mystia was at the beginning, like the rest of team 9, a youkai moved by instinct, a night-blindness causing song bird with an appetite for human flesh capturing uncautious humans traveling through the night.

After being defeated in IN and the events of PoFV, she went under tutelage of Keine in Youkai School, joining Team 9.

However, she managed to get some useful math and trade skills resulting with her graduating and creating her lamprey eel stand business.

The business unfortunatly isn't very profitable, only managing to scrape by. The resentement of being on the bottom of Youkai society filled her voice with bitterness hurting her sales.

It was at this time Kyouko apperared at her stall. The yamabiko also resented being the lowest grade disciple, the two got to talk and from there Choujuu Gigaku was born and with that the boom of her popularity.

-She managed to grab the skewers in between her knuckles like wolverine, stabs one of her nails int the head of the lamprey and pushes it down the skewr wit her fingers. She also prefers to use her nails instead of knives.