I Want to Be a Receptionist in This Magical World, Vol. 5 (manga)

With a few more months of experience at the receptionist desk under her belt, Nunnally is off to the Seleina Kingdom with her friends for a well-deserved beach vacation. Nothing-not even another surprise encounter with Rockmann-will get in the way of their plans. At least, that's what Nunnally thought before being snatched up by a hulking fish thing and taken to the bottom of the ocean! Even worse, Rockmann swears that he'll rescue her, and she hates owing that smug playboy anything! But as Nunnally thinks back to all the times he's been there for her, perhaps the frigid air she's kept between them is warming...