Responses
As an autistic person myself, he could be on the autism spectrum as well! I´m always super confused when I´m in a relationship and I need my partner to exactly tell me what´s going on and how they feel. And I end up doing dumb shit anyway. ( ̄∇ ̄")
Not that I´m defending him or anything, and I get that Ume was afraid of being left, but in the end isn´t being honest much easier? Especially when you´re suffering anyway. ( ̄∇ ̄")

I'm glad so many other people are getting the "mentally challenged" vibe, because I was trying to decide if the mangaka was doing that on purpose or not. However, it might not be that he's delayed, and he doesn't seem malicious, so I wonder if his character is supposed to be somewhere on the autism spectrum. Social cues and norms are challenging for autistic people, and they tend to take others at their word. Because most of their communication is screaming and crying on Ume's part, and Hara asking questions that seem too obvious to merit answers, it could just be that Hara truly doesn't understand what he's doing wrong.
That being said, I still really hate the relationship that he has with Ume, and I hate that Ume just tolerates it, defends it, and acts like he has to give up everything and just live with it. I would love to see Hara feel some of Ume's pain, but I'm just hoping this doesn't keep being the same dumb lack of communication for the next few chapters.