Responses
I think he just doesn't want anyone to come between him and his ambition for his clan to rule the empire trough his marriage.
Since he does not love the princess I don't think he sees the bodyguard as a potential love rival but more as an other party who could influence the new ruler.
I meant to hit the like button
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Maybe if her fiancé had encouraged her feelings for him when they were kids, he wouldn't have to worry about the bodyguard now