The Prince Is Kidding Me.

Aoi is an office lady hoping to get married and live a "normal" life. On an Earth where a gate has opened to another world, her job is to manage the people who have come through by mistake… However, this demon prince from the other world seems to like her a lot! The problem is that he expresses his feelings by saying, "I'll make you my pet...!"

This is a slapstick workplace romance about a girl who is confused by the culture of the other world and a demon prince who wants to learn more about Earth!

(Source: Zero-Sum Online, translated)

Note: Chapter count includes two volume-bonus chapters.