Maybe it's that annoying "-ssi" tag.
In raw, Suha called “isanim” means Director
No suha address jiwoon with "isa-nim" which means director. If it's "-ssi" then it should be attached to the name and usually translated to just the name, but here it just said "sir" instead of "jiwoon".
Anyway it's just that in korea people address others by their title at work it's not easy to suddenly change and call someone by their name ig. Especially when they're your superior.
Welp, that's hella weird
Yeah they’re so polite even to their lover
They’re dating, but Suha keep caling him “Sir” is really bothering me and Suha getting prettier chapter by chapter. I love how the author really improve the art