I just want to explain Seungho's side since lot of people are hating on him (which I won't argue since he's a shit to Nakyum) but as a person who reads book about psych, it is really hard to overcome a mental trauma. Seungho has a mental disorder/illness probably from the past traumatic experiences that he had with his family (theory) and he's also a mentally unstable man. The emotions that he has been feeling for Nakyum is a stranger to him because he hadn't felt that since a long time ago so it was confusing for him. He loves Nakyum, he came to love him but he's expressing his love in a wrong way (possessive, abusive way). Abusive person and toxic relationship isn't justifiable. But from the moment this manhwa started, we knew that this wasn't a normal one which contains unicorns and rainbows, instead this manhwa contains the dark theme so the perfect relationship that we've been waiting for, unfortunately, we can't get that soon. Seungho's character in the latest chapters is due to the abandonment thay he felt when he thinks that Nakyum ran away from him (we can't blame him for that because Nakyum was threatened not to spill any info). So as a person who knew nothing of the correct way to express himself, he was left no choice but to be an abusive person to Nakyum.
"I came here to get a tattoo but got pricked by different kind of needle" ahsjjsjsjs
By the way I need that next time! Switch please sjjsks