They fucking like mortals, I've read hundreds of novel about cultivating immortality and there sex is almost non-existent. This whole game gives the wrong impression about this whole immortality cultivation.
What ones you reading? Their is a lot of them with them having girls and I mean a ton! I read manhwa and manhua all day long.. reading about 30 right now since it takes some a few days for a new chapter while some take a month.
Evil or Self Satisfying Cultivators rape woman for pleasure.
Other Cultivators have romance with woman for love/pleasure or both
Dual Cultivation they do it for the benefits gained from it as well as the pleasure
So yes you can have sex in cultivation without it being rape.
Dual Cultivators especially as they will use charm and make the other sex want to have sex.
Cultivators fight with their lives on the line they know that if they duel and lose they have bet their bodies if they are lucky it's just sex and if unlucky they will be killed. This is why when they have a grudge it's not a spar it's a Life & Death Duel and if they lose their lives are owned by the winner. They know when they win the rewards are great they are dueling to ultimately become an immortal and with his risks comes high price of losing and so if they lose they are at the whims of the winner.
They will do what is necessary and hope in the future they have a chance to escape so they do not call it rape as they willing submitted when they took on the Life & Death Duel. So unless it's a cultivator raping a mortal it's not called rape it is strength that determines everything and if you lose you are now owned by the owner.