I think it's rude to call them by their last name when they both call me by my first name...

For the sake of team unity, wouldn't it be friendlier to call them by their first names...

But I don't know about such a calculating reason... It's more disrespectful to both of them...

Aa..Hiori-chan..

...Cute....

Aa...!E...

A!

Well, Ms. Sakuragi.

Good morning...!

Aa...Uuum...!

Good morning, Hiori-chan.