No they don't if they don't consider it to be an important thing. Easily can be forgotten when you've lived for many years.
I wouldn't consider this as a normal relationship either. Obviously, the guy was getting too pushy and now he's raping him.
I understand but when do many things specially these kind of things no way you won't remember the person true you won't remember everything but for sure you will remember a little! And from the story we can tell that they didn't spend only a short period of time together
We didn't consider that maybe the seme perception of their past "relationship" wasn't what actually happened....the seme is pretty fucked up so I would keep in mind that option
I can't believe that dohyon did forget all those things that he did with sangwo in the past,,normal people will remember these things unless he dose these things with guys a lot so he can't remember or he lost his memory in an accident but from what I see they spent a lot of time together and did many things how come the uke can't remember!,, and why did he leave sangwo their relationship was fine