It's manhwa, so Korean. There's a love triangle, but no threesome (as far as I read)
Psychological, quite a lot of TW, the story is dark. The ML is threatening MC about MC liking their friend (IIRC), and using him as an errand boy.
I remember the first chapter was the MC running away from ML half naked with a collar on his neck.
Also there's a scene where MC works at the bar while being sick