Okay, you said you are simplifying it but you simplified it a bit too much. Jinwoo's issue isn't that Daehan was helping his "friend" with the love letter but that Daehan chose to sacrifice their time together to do so. Daehan and Jinwoo spent a good time by themselves at Jinwoo's place right after they started dating. But they couldn't meet everyday bc Daehan had to go home too, however everytime they did meet it was an undisturbed time together. Then Jinwoo moved back in bc he wanted to see Daehan everyday even if it meant they had to give up on being intimate for the time being. All was good until Daehan got into his head that he wanted to play guitar for Jinwoo on their date. So he sacrificed a bunch of time they could have had upfront and spent it with a shady guy. Jinwoo never said he liked guitar or found people who play guitar hot or any indication that he even likes guitar at all. Daehan just wanted to do it bc he thought Jinwoo would find it cool and he did until he found out who he was spending time with. Ofc Daehan considers him a friend but he is also dating a guy this time. Yes, it is both their first time dating a guy but Daehan has a history of being inconsiderate to his partners and then got truamatized by being dumped by them. He hasn't worked on it truly and this time he is projecting instead of trying to resolve the issue. He did work hard on communication initially bc he didn't want to blow up this relationship but he still ended up doing just that.
Yes, Jinwoo blew up, he is only human but he also said he wanted them to take some time and work their feelings out before talking it out but Daehan missed that part bc he was busy projecting that Jinwoo will soon really dump him.
Tldr: Daehan's main issue is he doesn't consider what his partner wants or communicates with them, be it Jinwoo or any of his past partners. And this time he stopped communicating right when he needed to. Smh.
This litreally THIS you ppl need to chill the fuck out and accept that relationships are sometmes complicated omg
"and this time he stopped communicating right when he needed to." clock it. even if we set everything else aside and extend some grace to daehan, it is unbelievably ridiculous of him to simply block out everything jinwoo was saying and instead come to his own conclusions about what jinwoo was actually saying when he couldn't have possibly been more clear. and then he literally ran away and proceeded to discuss his relationship problems with someone else instead of his boyfriend. so much for being communicative, i guess!
Guys... Jesus Christ. It's both their first time dating guy, but think about it. Daehan is surrounded by dudes being bros and being clinging faaaarrr more than Jinwoo - especially as a student athlete!! I played softball in HS and let me tell you, you could not fkn tell if some of us were dating, fkn or just friends with how buddy buddy people be, even when they're already in relationships. I totally understand where Jinwoo is coming from. But if he didn't even talk to him about it when it was already becoming a problem and straight up went into "let's take a break" mode, I think that's also a big issue. Daehan can't come perfect guys, I thought we loved how communicative and expressive he is??? How open he was to Jinwoo this whole story and how he did most of the chasing from the beginning? And now he makes a mistake and we're turning on him? I don't know... I feel like that becomes unreasonable, it's not a good look, but Daehan isn't doing it maliciously, why are we punishing him for being ignorant of feelings Jinwoo never shared until he bursted and said something that I don't think was appropriate for the level of concern/lecture they had (taking a break because he was what, too jealous at him for being too close to another dude he considered helping him/a friend at the time? Im likey simplifying it, but thats how it seemed on the surface)