Princess of the Moon: Allure of the Midnight Kiss (2016)

Welcome, Princess of the Moon. You arrived at a negotiation in a foreign country with remnants of the Middle Ages. Night has fallen by the time the negotiations end, and you wander into a palace as you follow the moon home... Suddenly, chosen by the Princess of the Moon, you are to choose the next King that will lead the three kingdoms--!? Before the fated day, you are to live together with the prince for 3 months and take lessons to become a true princess. Furthermore, you have to perform a secret role to the princes on a night with a full moon...?! Which prince are you going to choose?