Call him Taehyuk, Hyo-Un ;_;

Maybe because his memories of taehyuk from their past life returned. And from his memories, he calls him sir

Yeaa, I get that but seeing him call him that in present life is sooo not romantic ╥﹏╥

Yes I get that totally T. T

I think its more like tae hyuk is so dear and big of an existance to him that he doesn't dare calling him on equal standing yet.

I think it's a bit of a translation fail - in Korean he calls him 'nari' which is an archaic bit of the formal speech form

Translation yoinked from the internet:
나리 • (nari) - archaic, term of address used for persons of high rank, similar to sir, your honour, my lord.

Yet he fucks him like a ragged doll. Lmao, the author's hierarchy is upsetting if its so
(≧∀≦)

....this made me laugh like a little goblin xD