Would love a futa for one of my girls. Have a couple of ideas under the cut.
The Arranged Marriage
Young woman(early to mid 20s) from a Conservative Christian family/community, essentially set up for an arranged marriage. She is not happy with an arranged marriage, nor her parents choice for her husband. Though not usually her scene, she goes to a bar/club to drown her sorrows and meets your girl(another patron or a bartender with a sensitive ear). Fucking ensues. Not required, but would be a fun angle if inter-racial. Could play the fall out for when she gets pregnant and the child is clearly not the husbands.
Hot for teacher
Student(Either High School or College) gets more than she bargains for with her teacher/professor. Could play it out either with my girl actively flirting with her teacher and bites off more than she can chew, or can be a bratty know-it-all type that teacher decides she needs to read less, fuck more.
Work Rivals
My girl and your girl are competing for the same promotion at work. Your girl wins. Reassigns my girl as her PA(Personal assistant or Piece of Ass, lol) and proceeds to further establish her dominance by fucking her and eventually having her carry her child.
Twincest
Twin sisters. Though my girl knows about her twins "extra friend" no problems ever occurred. Until now. Girls are left home alone for a week while parents are out of town. Your girl decides to take advantage.