I don't really like slutty heroine because it more NTRI then NTRE
The story can be simple as MC give cursed ring to Priestess and find a way to cure it and met with yarizo you know go to adventure guild find information go to dungeon bring yarizo for ntr and go back to town
or
MC and priestess met while MC or priestess tried to find something(items person etc.)so they set off on adventure together met yarizo on the way
or
do something with The dude in the castle? king? like make a request to the guild member to take care of somethings or do some dirty work
BTW while typing this Karryn's boob keeps bouncing around make it hard to concentrate