Dong-Young is the princess of Heaven who must wed the King of Hell to fulfill a peace treaty between Heaven and Hell. Unable to go through with the arranged marriage, the Princess flees to earth and hides herself as a typical teenage boy. The queen orders the Four Guardians of Heaven to find her but the Queen knows something she's not telling...
A school is going on a field trip! It happens to be the same school where Dong-Young and the Four Guardians all secretly attend. When Dong-Young falls into some trouble with a water nymph, Ah-Hin finds out Dong-Young is a she! Bur unknown to Ah-Hin, he that's a she is the princess, but Ah-Hin promises to keep her secret as Dong-Young continues to act like a guy.
As Dong-Young finds out that ALL Four Guardians attend her school, she must be even more careful about her disguise. As more and more people come to search for her, Dong-Young has to be even more careful.