
Is the tonic they made NK drink for health reasons or for sex boost? I read a trans for chap 36 wherein NK doesn't what to drink it anymore because he thinks it makes his body strange? Or the reason he feels strange is because his body involuntarily craves for sex because of the numerous times they did it?

Honestly, in my opinion, it's a little of both. I mean, Seungho is also taking this medicine and sometimes he is not in the mood like in the previous chapters with Jihwa. And as we know, he had trouble getting a hard on without getting sucked on first. With Nakyum it's a little different.. He gets aroused by every little touch just like in the raws (spoiler alert) that salesman grobbed him. Seungho noticed how he went red and blushed by that specific touch which wasn't from him. So the medicine plays a bit of a part as well. Why else would he get erect by the slightest touch from anyone? In the end, I wonder...

I've been wondering about the colors of their clothes in chap 35. Somehow NK's usual pink one is now a bit darker while SH's is green. Maybe it's because NK really lost his innocence(not just his virginity) and a new door opened up for him and SH's green may mean greed or jealousy. It may also mean renewal or something because something inside him changed. Or they just picked random colors.

SH's first green robe had to do with greed, then being apologetic, then being greedy again.
I think this time it has to do with both greed and jealousy, but especially the latter.
I second your opinion on Na-kyum's darker pink robe and am looking out for whether or not his headband appears anymore or how it changes.
I want a Yohan in my life.