It's difficult enough for a young mutant prince to choose between the hand of the princess of the sea dwellers and the prince of humans. Add one begrudgingly attractive assassin and a handful of curveballs and you've got yourself one hell of an issue.
I know there will be some misconception, but this is not a "Karkat is a highblood now" story. All of that will be explained. Just know that he is still a mutant blood and the rest will come later. Enjoy~