[Shyni]

Originally Posted by GenjiChan

Sempai, Sensei, Onii-san, Onee-sama etc...

Calling your girlfriend or boyfriend with these titles and not using their first name. Why? In school, I guess but even when outside school or alone together?Is it cute?

Could be, although the only example I can think of that fits is from a non-anime show. Specifically, Kamen Rider Double.

Spoiler for Kamen Rider Double romance:

Terui pretty much always calls Akiko "chief" or something like that, even during one of the post-series films, during which they were already married. Apparently he always views her that way, or something. Might be cute in a intentionally ironic kinda way, since he's a superinendent(?) of police, while she's the employer of a small detective agency.