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

It's been two years since Nunnally started working Harré as a receptionist and it's going great -- she even has a junior coworker now! But on a trip with friends to a beach in the Kingdom of Seleina, they bump into none other than Prince Zenon...and Nunnally's archrival, Rockmann. The two are here for an investigation, though things take a turn when Nunnally is captured by a giant sea creature!