People coming up with theories about a different universe or the brother's haircut changing... the brother's haircut seems to mirror itself on the same page that he's introduced, this mangaka has a poor grasp of staying on-model. I don't mind it overly much (they rely on different hairstyles to distinguish between characters), but it does make it hard to tell designs apart, and it means you can't really rely on stuff like "this person looks like a different person in profile" or such continuity errors to make judgements.
The thing that says they swapped to an alternate universe is the fact that they said, in the manga, "we are in a different universe now" (well they didn't literally say that... but you get the point). We'll see how they handle it, whether we have a coming-back arc or not. I don't really mind all too much either way.