Lokheun's name means "happy morning," but her life takes a tragic turn when her mother is murdered and her father becomes a fugitive after exacting revenge. To save him, Lokheun devotes her life to Garyun, the dashing emperor who's committed to right the wrongs of his father. Believing Lokheun to be a boy, Garyun is determined to mold her into an unsurpassed martial artist, even if it means sending her to hell. Their strained relationship turns into something more as Lokheun searches for the one thing she's never had: a life befitting her name.