Aphonic

But his name sounds kinda like sangwoo (I'm sorry I don't mean it)

That’s what I thought too

I thought so too. Not exactly autistic since I don’t know the exact symptoms but he shows signs of someone who is neurodivergent...

i doubt is autism, but problems with faces and names can be caused by ADHD and that's probably the motive he follows a routine and is so easily distracted. when you have ADHD one step out of your routine means you won't have anything else done for the rest of the day (or it sure feels like it). but anyways i think the author doesn't intend to introduce anything like this to the story (even though he mentioned a doctor before).

Yes I think he is. Autism without intellectual deficiency (sometimes called Asperger) as you pointed out: trouble recognising faces, love and need for routines, appreciates loneliness and calm and dislike for noise and interactions that he doesn't want, no need to have many friendly relationships but satisfaction with his passions, very honest with himself and with others... from my point of view there is no doubt at all.
Note for people who don't know about Autism: it's a spectrum there aren't tightly closed categories its a continuum from "neurotypical" to "neuroatypical" and people have some symptoms and don't have others. And from the perspective of many people it's not an handicap but a difference (neurodiversity) and even a quality.
Like, you can find a lot of Aspergers in activism and devoted to research or advocacy on complex issues, because they can be more willing to question themselves, question social norms. And although Sangwoo isn't very communicative and passes very strong moral judgments, many Asperger can be very open to discussion and work well with people when they have similar interests and common projects. Just to break some myths Autism isn't like one may first think.