Yeho, an impoverished distant relative of a small kingdom's ruling family, becomes trapped in a desperate scheme when the North Empire demands Princess Sooyoung serve as concubine to an aging Emperor. Though the king treasures his daughter, he commands Yeho's older sister to masquerade as the princess instead. After convincing his sister to escape with her lover, Yeho is left alone with his gambling-addicted mother. When he attempts to return the king's compensation gifts to cancel the arrangement, he discovers his mother has already squandered them on debts. With no other recourse, Yeho devises a bold solution: he will assume his sister's identity and journey to the North Empire himself. Arriving at the imperial court, Yeho plans to reveal the truth and eliminate the Emperor. His scheme falters when the sovereign embarks on a tour through his realm, forcing an unexpected delay. Upon the Emperor's return, Yeho's carefully constructed deception unravels—not from discovery, but from a shocking revelation. The Emperor is far younger than anticipated, transforming a calculated assassination into something altogether more complicated. As the gender-bender plot deepens, romance emerges from the ashes of cold calculation, ensnaring Yeho in a twisted destiny he never anticipated.