People get why he was hurt but just like you said, his ex also played him so of course hang out with the shitty ex (who also have intentions to break you up with your boyfriend)is not the right choice. If he just drinks with his friend or his sister no one wouldn’t mind.
Well, his action is understandable, at that moment anyone would do and his ex just happened to be with him. but again his ex should be the last person he drinking with.
Bruh ya'll really dont get why Hajin is pissed? He had no idea why Hangyum would kiss him then date another girl like 2 hours later. Of course he'd say he hates him in the heat of the moment! Then, Hangyum left without a word. You'd probably miss someone so bad you practically forget about everything you said in the spur of a single moment of the several years you spent with someone. On top of that, ya'll have never been so desperate for company that you'd settle for anybody? He was beyond broken and shocked, he was played by the same person he'd longed for, TWICE. In his mind, he's probably confused and angry. We shouldn't switch up on Hajin just because he's being a messy human being! Let it out king, and then reflect and talk it out. TRUST THE PROCESS!