I kinda hate how each of those braziers in the cave seem to be linked to an individual girl and not the overall corruption of the village.
When the second brazier lit up shortly after Marin had sex with Enlai i was still under the impression that it IS for the overall corruption, but then the 3rd one got lit when Violet had sex with her father-in-law for the first time, and right after that the 4th one turned on while Yui was having sex with Dukall, and so yeah, it's pretty obvious now that each girl is linked to a brazier, or i guess the girls are not linked to the braziers specifically, but rather 6 girls are needed for the ritual to work and those 6 can be anyone.
As for who the last 2 girls are...nobody can say for certain but i guess the obvious choices are the blonde priestess and Kema's mother, and i'm gonna be honest here i hate both of those characters, or i guess i don't hate them, it's just that Inatari has been ignoring them since the very first version of the game and so it's basically impossible to get attached to them, i straight up dread the idea of that priestess getting any screentime cause i just think that it's a waste of time that could've been spent working on the 3 main girls. I don't mind Kema's mother getting screentime but the thorn in my side there is the guy that's gonna corrupt her, that Blacksmith guy is NOT a good character by any means and i'd much rather see Ryuu's grandpa corrupt Kema's mother as well because of how she's Violet's best friend.