I kind of dislike Natsuno so far. I get that he didn't lie about the relationship just to get a place to stay. It was more because he was sad, and had some feelings, but most of it was just because his ego was bruised.
While reading, I was thinking something similar as well. The way he says "how can you forget the guy you confessed to?" while irritated makes it seem like he feels as though Ui should've remembered him forever and that it irritates him that he's not that big part of Ui's life still. Though i can also see that he's just dense af and doesn't realize he has feelings for Ui.
I feel like rather than one or the other, it was both. I agreed with Ladybelle, but i also agree with what you said. I think at one point (the beginning), it was portrayed in a way on purpose that made you think he was a bit of an asshole because it seemed like what Ladybelle and I were talking about, then it went on to add another layer, that being what you were talking about. He seemed to just be butthurt at 1st about not being remembered, the way he talked/thought about it implied it was an ego thing, then his thoughts started to imply he was actually in love with him and that's why he's upset he was forgotten.











So glad they confessed and worked it out and they didn't drag out everything for multiple chapters.