Cuz his lover/boss is dead.
Well they weren’t in a relationship so both of them are allowed to sleep with whoever they want and how many they want. And the uke is sleeping with the other guy not because he wants to but because he needs to. And since the one the seme was in love with is dead he didn’t really have any interest in sleeping with other people surely at first he slept with the uke cuz he was his boss and that’s what he demanded
I mean of course they're allowed but that doesn't mean other ppl want to see it also the uke is legit the one who suggested sex for info in the first place up till then he'd been getting info without it
Well at least, he’ll stop sleeping with other guy. Not just MY cup of tea where uke sleeps around with other guy. While the seme is sticking to one. Tho seme seems to be in love with the dead hyung. But seme only sleeps with one.