lets not forget how he wants to wed his sister to nok for "protection" even though all of nok's bride died. like it was weird how he put his sister in a dangerous situation like that. he even said something about his position when he saw nok with jaeshin. i presume he thought his position as nok's right hand man will be taken by jaeshin.
Your right I do remember side eyeing because clearly Nok told him his previous wife’s had died and he doesn’t want to put Kyungjoon sister in any harm but that asshole was completely okay with it as long as he can give power and protection to Nok like what?! Him siding with the Queen kinda proves he never considered Nok as a true best friend/protector more as a tool he can use to gain his own power.
We knew Kyungjoon was homophobic i didn’t even think much of it because him and nok are childhood friend even in his flawed view JUST MAYBE he wouldn’t betray nok but boyyyy I was wrong also I like how the afterworld seem much more “peaceful” than that darn palace.