i think the other guy was just his sex friend. he should have ended the relationship when he started going out with mc. i didn’t see ml sleeping with redhead anymore after ml started dating mc started going out.
mc seems more angry about the past; ml was probable his tutor and left without telling him or something.
not sure about it though since i don’t really understand korean! hope all is good > <

I looked at the raws because some one said the seme was [1] the main boi and i was like he cant seriously be [1] the baby and omg not only was he [1] but also doing so much more worse stuff and i no longer root for him
[1] = two timing
Not only was he two timing at the begining of the relationship but he was also lying on another way more important issue later on 40ish its revealed thag the seme was the ukes first love (? I think it looks like that) and was is tutor but broke is heart (again i dont speak korean but given the tears it looks like that) and the main baby finds out by going over to his place to wait for him and finds the semes high shool yearbook and looks at it (seme looked at his prior to this so why not) and sees the picture of him and realises their past connection and wants to leave he is sad obviously. And then he walks out to run into the seme having an agitated verbal dispute with the dude he was two timing the main baby so that seems to have been revealed in this whole shit show of a moment so yeah sad
*i take no responsibility for my false interpretation if everything i just said turned out to be horse shit, sorry