17th century Joseon. A foreign ship encountering a violent storm is shipwrecked at sea, and a young man, Guest, who was on that ship, is washed ashore alone on the coast of Joseon.

Summoned to the palace for being a foreigner with an unfamiliar language and customs, Guest meets Seong-hwi, the King of Joseon. While showing interest in Guest's knowledge and skills, Seong-hwi promises the necessary help to repair the shipwrecked vessel so that Guest can return home safely.

Thus, while the ship is being repaired, Guest stays in the palace, teaching the technology and culture they know, while Seong-hwi also teaches him the language, lifestyle, and culture of Joseon.

At first, the two were just a stranger and a king, unfamiliar to each other. However, as the time spent together grows longer, different emotions begin to take root in the relationship that started with simple curiosity.