Honestly I like this, it's very straightforward. There is room for them to eventually develop feelings as they get to know each other, right now they're doing things for their own benefit and just that is fine. One cares for the mountains and the nature he's protected and the other cares for his only family member whose been there with him since the beginning. Losing someone is one of the worst things a human can experience, I'd totally give up my ass (if I were someone with a dick) for the life of my loved one. That is a small price to pay.
It's kind of funny how dry the sex was, not just with prep but also with the atmosphere. They're like "well time to try to get hard and get my dick in there, lemme just... jerk off and shove it in" LMAOOOOOOOOOOO At least taesun was smart enough to use lotion (idk if it was lube or literal fucking lotion which would do nothing) to try to prep himself better but they both need better experience. Damn I'm surprised he wasn't fucking bleeding!