That exactly is what he is trying to avoid-- yoon drinking nux's blood. Because if yoon does drank it, he will be a pureblood and when he becomes one, jooyoung will take yoon in the place of vampires (maybe another country etc) and live with him. Jaegyon (the guy holding nux blood--can't remember his name) likes jooyoung so he cant afford to see him living with yoon in a faraway place. It's like he can't take it if jooyoung left him for yoon. So the only choice he got to avoid losing jooyoung completely is too offer nux's blood to the director and have his blood cure yoon. Through that method, yoon wont be a pureblood and jooyoung wont have to leave with yoon.
For me, that's the best solution thus far for both of them. Yoon will be able to stay with the director's side and depend on him like they both want. And aside from that, jooyoung is somewhat free from the guilt of his past if you could say.
Hope you'll understand my rxplanation coz I really suck at storytelling. (￣∇￣")
I love this. Art is and the xxx scenes are But. Couldn’t that guy have just given the vile of Nux’s blood to the sick boy and make the new Nux boy happy with him again? Instead he gave it to the director... so now the sick boy has to drink the directors blood forever, instead of being completely healed and a full vampire? I get that it’s “for love” but it’s just saving the boy with extra steps. You feel me??