This is a once-in-a-lifetime opportunity. The deadline is one month. Assassin Sa Cheong-ok, tasked with assassinating Prince Yugeum, infiltrates the palace under the guise of 'Wolhyang,' a position that teaches how to handle women. Although it's his first time experiencing such things as a man, he gradually falls into an unfamiliar pleasure of spending nights together... 'I want to do something even more enjoyable.' As they spend nights together, Prince Yugeum, rumored to be a ruffian, also seems to gradually open his heart to the assertive Sa Cheong-ok. Will Sa Cheong-ok truly succeed in his mission?