
I bet the prince is actually a princess.

Let me break it down again.
Crown Prince = old faction. Bad.
Second Prince = new faction. Good.
Women = Bad. Can’t inherit titles. Can’t lead. Can’t be knights.
So second princesss is made into a prince to lead the New faction.
So it’s crown prince vs second prince to see who will be the next king. Likely assassinations could be involved.

Is this a green or red flag romance?

so far there hasn't been any romance, it's just a transactional relationship for now. if you're talking about consent, i would say it's relatively green? the top isn't a human so he does get a little bitchy during sex. whether you consider him green enough for you, you'll have to decide for yourself. there is no sexual violence.
Every time I see this comic update it feels like that meme. “Ah shit here we go again.”
Because we all know he’s still gonna stick around cause he gets caught getting railed by the manager later on. Which I hope and pray will be the true last straw (it won’t).