Well, it's normal for couples in at least Korea and Japan (don't want to speak for other countries as idk about them lol) to refer to each other formally for a little while in relationships. I don't think it usually lasts that long but addressing a loved one with their first name can sometimes require permission and pretty much signifies that they're super close to each other to be able to address each other casually. Not only that but the prof is still Hansol's actual professor so it can be seen as rude to address him using his first name despite them dating. And with the prof being a "boomer" and still being his professor, idk whether he'll want him to stop with the formalities until he's no longer his student... does this make sense?
Anyone else is welcome to correct me if I got something wrong :)
Then again the prof said those three words so who knows whether in the next few chapters the prof will ask him to address him casually in private
I wish he’d stop calling him “professor” and actually call him by his name. I honestly don’t like this trope but it happens so often. Like, y’all are literally dating each other, pls, for the love of god, stop calling the other person by their work title I can see doing so in public and in front of others, but the fact that they continue to do so in the privacy of their own home kills me T-T