Sieun not hitting bumseok is a genius move actually because bumseok since the very start of that fight scene where sieun is just relentlessly going after the two guys who were part of what had happened to suho, sits still on his chair, preparing himself for the inevitable. He knows sieun is going to go after him last, and when he finally finishes, it’s clear that while he thinks he deserves it, he really just wants to get the entire thing over with. (Shown through: his repeated lines before Sieun had pushed him off the table were: “Just hit me.”) If Sieun did end up hitting Bumseok (and I can believe that Bumseok is going to /bleed/ and /bruise/ so bad if Sieun did and it would probably take a bunch of teachers and students holding him back to stop him from continuously bashing bumseok’s face in), it would probably make things lighter for him. Maybe he’d think that “the worst is over” and he’s already gotten what he deserved, so he can move on with more ease. Like a weight lifted off his shoulder. He did horrible shit, he got what he deserved for doing horrible shit, the wounds will heal, and even though he will be tormented by the thought of Suho every once in a while, the guilt wouldn’t be to the same extent he’d feel if Sieun hadn’t punched him. Mind you that if this is what had happened, Sieun would probably feel absolutely horrible after too, probably even more than Bumseok. Because that’s just how Sieun is. And that would be the worst thing ever.
But Sieun didn’t punch Bumseok. (Thank god, but not for the reasons you think haha) He couldn’t, even if he really wanted to. We could get into the Sieun’s side of things but I wanted a spotlight on Bumseok’s more, so, short summary of Sieun’s side: he has a big heart (“you’re so warm hearted”), Bumseok is one of his first friends, he will never be able to forgive him for what he’s done but he also really doesn’t want to believe that Bumseok would go that far even with the real and tangible videographic evidence presented by Yongbin’s phone. Because Sieun /understands/ Bumseok, even when he really doesn’t want to (this understanding can come from different things, in my opinion. From the feelings for Suho or the loneliness coming from the lack of a real family..? Not sure).
But what does this do for Bumseok? Everything. The way he will live his entire life after that, coming out scot free from what he’s done because Sieun, the person he’d probably hurt the most other than Suho, refused to hit him. I’ve emphasized the fact that Bumseok was already ready for the hit and wished for it just so he can get it over and done with, and with Sieun denying him the inward satisfaction of getting what he deserved, it will leave him with that scar forever. That is by far the cruelest thing Sieun could ever do, even if he doesn’t know it and he was acting out of the goodness of his own heart. Because then Bumseok would be left searching. The cycle of his abuse remains open and he will probably begin seeking personal redemption, something to take the guilt off, by either getting into fights and allowing himself to get hit. Or just straight up letting himself get beaten up. You know how some characters pick a fight and then it’s revealed/implied they only do it just so they could get hit? (I don’t know if that’s a common trope but I’ve seen that a handful of times) Or he could seek it in other ways and just drown himself in his own self pity and the crushing weight of everything he’s done on his shoulders. There was nothing to take the feeling away, because Sieun never gave him closure by refusing to give him the beating that he so deserately craved and deserved. It will haunt him. Bumseok will never be able to move on for the rest of his life.
