For a lot of people who were chronically sexually abused, sex is actually the best cure for them. That saying of fighting fire with fire didn't come about without merit. While it's definitely important for Geom to feel safe and secure outside of sex his biggest issue is dealing with the intimacy of sex and learning that it's not a currency. The only way to do that is to have sex with someone who is doing to with him purely for love and affection and expecting nothing in return. Being rejected in a sexual manner could be potentially devastating to his psyche. He's literally used that and had been taught to use that his whole adult life in order to get what he wants and to survive. To have no goal attached to it can leave him fumbling and lost. So having a sexual relationship with the right person can help him cope with that trauma and rework the way he views sex altogether over time.
The raws are now in the redemption "light at the end of the tunnel" part. But i cant feel any joy from their relationship... the chronic rape of Geom has taken away any sensuality of their lovemaking now. I would have preferred if they showed a still romantic but nonsexual (yet) development for a few years between the two. But the marathon of gangbangs and the author depicting Geom as a "pretty" sex slave through all those depraved chapters.... you just cant erase that as you read their supposedly "pure" newfound relationship.