Boy Princess, Volume 1 by Seyoung Kim
Boy Princess is a pulse-quickening tale of swords and sorcery, far-away kingdoms, and the fairest princess in all the land... with a twist. When a prince's soon-to-be-bride elopes two days before their wedding, her desperate family dresses up their youngest son and sends him to get married in her place. With his pretty blue eyes, cascading blond hair, and strategically placed apples, nobody bats an eye at the pretty pubescent standing before them. But how long can he keep up the charade? Despite odds against them, the two princes share adventures and intimacies in this mesmeric offbeat romance.