Yongcheonru, the largest inn in the Joseon Dynasty, operates under the motto "The Guest is King" – challenging the strict social hierarchy everywhere else in the kingdom. Four trainee servants work at the inn, all from different backgrounds and with their own goals: Lee Eun, a prince hiding his royal identity; Hong Deok Su, a woman disguised as a man; Cheon Jun Hwa, the unwilling heir to Yongcheonru; and Go Su Ra, from a merchant family that's losing its status. While working through their trainee period, the four young adults face new challenges and form close relationships, all while trying to develop their own senses of self and upholding the inn's unconventional standards.