Probably the hair is pokeing the clothes

The typical solution to that is to dforce hair and clothes seperately. 

Uhg..... as someone that spent a crapload of money going down the Demonslayer hole last fall, and in terms of simplicity, I'd recommend: https://www.renderhub.com/dumitas/rumi-for-genesis-9 and https://www.daz3d.com/dforce-morgan-hair-for-genesis-9 for Rumi. I personally used dumitas's genesis 8 version for Rumi and manually scaled and parented the hair.
On a side note, Dumitas's Rumi has a rigged tail, makeup options and a couple of geo shells with the "patterns" though the patterns aren't nearly as detailed as what you'd see in the movie.