Nico looks embarrassed at getting carried away while Honoka is just sheepish about the whole thing. I mean, that is a pretty exposed spot for a bite mark...
DIANA: W-well then, you watch me now as I show you how it's done.
AKKO: O-okay!
DIANA: Just slowly rub your hand on my back ...
AKKO: !!!!!!
DIANA: I-IT'S for the sake of the enchantment and d-don't stop until I said so!!!!