Responses
Adding the factor that he is a man making him more afraid
Society isn't exactly accepting of that homos in that era so he's thinking of the hardships they'll go through will hurt seme and that hardships won't happen if seme ends up with princess
Also, the fact that he is the crown prince which means he's obligated to have a child
Well I think mc is just afraid that the future ending with the hero and princess will come true...
I think he thinks that "I'll get hurt in the future if we continue this relationship so I should end it now" "Sure he likes me now but what if it will change later because of the princess"