A large variety, but rather not the usual rpg:
"sweet talk and gift her through chapters 1, 2, and 3, and you'll get a kiss and pledge of undying devotion in the end of chapter 4"
rather something like:
- platonic deep bond through shared hardship.
- mutual affection, either turning into love through time, or not
- just get drunk the day you meet and conquer his/her butt while he/she's passed out.
- lonely people on a hopeless quest, occasionally sharing the bed
But don't make it necessary to partake, and don't do those "oh, if you didn't pick the "line b" in chapter 2, the subplot ended right there.
It just seems improbable to trek around the countryside for a year with this omg hot hot bikini elf babe you picked up from the dark fortress of leather and whips,
and it'd actually never come up that maybe, just maybe, you'd like to...