Well, I think people are calling him autistic because he exhibits very rigid behaviors. For example, the scene where the uke asks him if he's not going to sleep, and he interprets that question as an invitation from the uke to have a hot night. If it were only that, it wouldn't be rigid behavior, but the expression he puts on his face, as if it were something they both have to do out of obligation, as if it were a job. Other signs that show cognitive rigidity were when they met. He wasn't even bothered by the misunderstanding. He was on a blind date somewhat out of obligation and not in search of a partner. Or when he took the uke to meet his parents, or when he stayed with the uke on the date the uke had with his friends. Very rigid behavior, expressionless, it seems like he's in a separate bubble. I think that's why.
I see some comments said the top is autistic. I can only imagine autistic trait in serious term lol and it's kinda hard to think he is the same autism that I know. Tell me what's the meaning of autistic in this manhwa (×∆×)