Isn't being a gay couple normal in this world? Our mc is way too dense lolol

Yes, a gay couple is just as normal as a straight one in this world, but Duagian was straight since he was a kid and came out as an omega male a few months ago... This is all new to him.
Until now, he saw Lu-ge as a friend; you have to keep in mind that Duan was a beta straight.

Yes, that does make sense in understanding his mindset.