I don't know if the translation you are reading has issues, or if you just misremembered and still wanted to spoil it. Anyway, I want to correct three things here:
1, Yohan didn't actually beat Jun. What happened was Yohan held Jun's hand too tightly because he couldn't control his emotions. In fact, when Jun tried to run away, Yohan was the one who shielded Jun with his own body so Jun wouldn't hit the floor.
2, Yohan misunderstood Jun's intentions when Jun tried to bring Yohan closer to Yohan's family. However, Yohan didn't need a mediator, and Jun also admitted that he acted selfishly without considering Yohan's feelings. Jun never asked about Yohan or asked for his opinion. That's all there is to it.
3, Jun believed Yohan's sister and called Yohan a liar. But if you read the side story, you'll see that Jun actually realized Yohan's family didn't love him at all. They abandoned their guardianship responsibilities to outsiders, and the housekeeper even talked about how Yohan's father treated him.
I really hope from now on, no one who doesn't even remember the story correctly will spoil it and make people misunderstand the information
Lets just go to the interesting part of the plot:
Jun starts to get bullied because of Yohan, being an outcast for a while. He even gets beaten up, with a broken arm by Yohan i think. It all started because he tried to defend Yohan on his family dinner (Yohan thought he was making fun of him??)
Anyway, after a while they become friends again, but its kinda forced. Another kid from school even warns Jun about Yohan being twisted but Jun doesnt believe it. I dont remember much details here, its just Jun living his days in tension and pretending.
Jun is asked/threated by some dude called Kim Mihoo (sorry i forgot his name but is similar to this) to confess to Yohan so they call film his reaction and spread to school. Jun accepts but in the moment he actually tells Yohan the dude was behind the curtains trying to film it. Yohan beats him up and dude gets expelled because Yohan made up some situation there.
Then, before graduation, Jun cuts off contact with Yohan because his little sister tells him hes actually really loved by the family, he even likes seafood and lied to him about being an outcast. I dont remember well why he does that, but I think his sister says that he just has some issues about really wanting to be loved. This whole time Yohan acts like this just cuz he wanted Jun's attention and love (??)
Theres also a part where Jun meets this highscool friend (i dont remember if it was before or after graduation sorry), but while theyre at a cafe together, Yohan appears and starts to act like an asshole and Jun finally acts, throwing a drink all over him, saying he hates him.
Jun leaves the country after graduation to think. He comes back to the country after thinking and starts college. Hes in the dorms and his roomate is not there, later on he finds out Yohan is in the same college (just different department) and instantly Yohan is at his door, hes the roommate lmfao.
Funny thing, Yohan starts acting like a poor sad dog, Jun tells him to leave and he just obeys, not before making a face like he wanted to cry really bad.
Someone starts to ask about Jun around college and he thinks its Yohan and calls him telling him to stop. Turns out it was not Yohan and in the middle of the call, that dude Kim something appears and throw acid at Jun to ruin his face.
Yohan of course appears and shields Jun, getting acid all over his shoulder which leaves a permanent scar on his back.
Jun feels really bad and from here they start being friends again. With Yohan saying he wont be a catholic anymore, kneeling and kissing Jun's feet, saying hes his new god.
After here, its just side stories continuing their days, at some point they start living together at an apartment Jun's parents got for him. And they have a really sexual tension, they have their first time together, and after this theres a few smut scenes. In the novel, theyre REALLY long. Yohan is basically pent up the whole time and the novel gets in real detail about how his dick is big LMFAO
Anyway, im still at the side stories now, happy ending i guess!
(￣∇￣")