That sounds like some redemption arc, and I’m in on it. I’d prefer if he loses his memory while running away from Sunghoe
This is just my little add on to your theory: Sunghoe keeps raping NK until the teacher finds out and for some reason gets killed because of it (I just want him gone tbh). NK runs for his life, goes into the woods, he trips and hits his head in some sort of rock. Sunghoe finds him bleeding from his head, carries him back to the villa. He treats his injury while he’s in a coma, then weeks later, NK wakes up and has amnesia. Surprised, Sunghoe leaves him in the room and realizes it was the perfect opportunity to make NK love him. He starts treating him gently, after lying that their lovers of course. We see a lot of lovey dovey shit, and when things are about to reach a happy ending BOOM ! Jiwha comes back to remind NK about what really happened, Sunghoe tries to fix it but is too late. NK kills himself... THE END

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So, do you guys think Nakyum might once again lose his memory due to fever and being sick? Or maybe not lose, but not remember everything well?
Everything leading up to him getting sick seemed to have happend in the course of what, past 24h -ish from the moment they had finished having sex. The violent scene in the pavilon, bath, chasing after Seungho with the sword, blowjob, running away in the morning, coming back and having sex till night or early morning next day. I wouldn't be surprised if he had hard times remembering all that, since it happened in the short amount of time, and, though very traumatic, coulde seem more like a dream/nightmare to him now.
So, could it be that Seungho might use that as an opportunity, kind of like a second chance, to approach him in a different manner, now that he seemes to possibly have some reflection over his behaviour? And it's not like I think it will be all love and butterflies now, nah :)) I'm thinking more like, he saw that his actions were troublesome and problematic long term, so he has to reconsider, if he wants to keep Nakyum for himself longer. There's still room for romantic developement, it's yaoi after all, but I'm looking at it from his selfish and entitled point of view for now.
Also, you know how old servant asked for some medicine for himself (if the fan translation were correct)? I'm thinking what he might use it for. Add it to Seungho's water to make him sleep, so he wouldn't hurt Nakyum? Or maybe that's just something extra to help Nakyum heal better/faster? Interesting