The Uke is an author and first approached the seme with the intention of using him as material for his manga character. The Seme has a lot childhood trauma and school trauma and always felt like he had put up a front. The Uke went after him relentlessly so he can get material and based his character on him and they started dating and they both fell in love. The seme found out that the Seme used him as inspiration for his story and he felt used and betrayed. And that’s when they broke up. The Seme did not feel like Uke feelings were honest.
You need a reread. Dohu did apologize, multiple times, in fact. The problem is this apology was prompted by Juheon, so Juheon does not believe it's sincere. Dohu's greatest mistake is not that he hid the truth from Juheon. His greatest mistake is that he, from the very beginning, never believed their relationship would last, hence why he initally was about to let their relationship go. Juheon doesn't just have trust issue, he also has abandonment issue. Juheon actually begged Dohu to love him regardless whether Dohu's love is true or not, but Dohu couldn't response because he didn't know if he should stay with Juheon. Only after Juheon left for good that Dohu realized his mistakes, hence why he was left to regret deeply for the next 4 years.
I haven't read the new season yet, but I was talking about the season before this one bro. Dohu's personality is not what you consider as normal, he doesn't feel like how normal people does. If you remember the scene before where he was with other people, he doesn't even know how was it wrong to use someone's "story" without asking their consent. And that part also where they had confrontation, he didn't even realize the principle behind what he did wrong. That's why when Dohu made some stuff so he can meet Juheon again, didn't Juheon said he should have apologized first? Juheon was waiting for that response but since Dohu is the way he is, he wasn't able to apologized and tell how he really feels.
Bro, lol. It's true that Dohu is low in Emotional Intelligence. They showed that many times already. He's not even aware of his own emotions. And is not capable of feeling emotions not until Juheon happened (hence why he was too late to realize that he love the ml) It has gotten to a point where his parent even want him to undergo therapy. That was his personal dilemma isn't it? He was also aware about it too. Lol.
Emotional intelligence (EI), or emotional quotient (EQ), is the ability to understand, use, and manage your own emotions, as well as recognize and influence the emotions of others. It includes skills like self-awareness, self-regulation, social skills, empathy, and motivation, and it is crucial for effective communication, building relationships, and navigating social and professional situations successfully.

Can someone remind me what Uke did wrong?