Oooh. How interesting would it be if he knocked her up, she loses her regal status as a prince and therefore ability to be come king... then the BODYGUARD becomes the king, and the Princess becomes the queen? The hottest and least violent coup ever pulled off!
The thing is, we don't know if she was the crown prince, or just an excess prince. Just as we don't know how she ended up a she (unless it's somewhere else and I missed it?) For all we know the King might be really happy about this.
I wonder what brought about the need to transport the Prince is such a manner? Personally, I'm hoping this all started as an elaborate prank that got out of hand.
Yeah, it's my interpretation that, when in male mode at the beginning of this scenario, our protagonist was the runt of the king's princely cohort, with the king of the opinion behing that they'd serve the kingdom better producing heirs as a princess. Maybe this king had produced so many male offspring that there's not enough princesses from other kingdoms for him to find one to match this particular prince of his with; so, he had his gender magically swapped. Maybe this king picked up hints over the years that this runt prince of his was effeminate and/or liked guys, and he decided to facilitate the manifestation of his runt prince's desires into reality.
As an alternative, maybe this king had had a bet about this prince between himself and this bodyguard, and this king lost that bet; and, the price for losing said bet was the gender-swapping of that prince, unbeknownst to that prince
