The thing is the previous Kim hajun doesn't have an identity so he's just a question mark, now he has an identity albeit not from that world. By him having a face it also signifies that he is starting to be a part of the story, all of this was technically implied like on the first 5 chapters if my memory serves right
thats true actually, didnt think of that! - i think it woulda been cool to see them work with it just because he wasn't there originally or even like he gets more features defined as the story goes on to show hes slowly being integrated more and more as a key character
i remember he has a ? face at the start and ngl it woulda been cool if they carried that concept over, really showed that he wasn't meant to be in the story