What do you mean by "my enemy and best friend"? It could be a mistranslation and he meant 'rival,' but to call Kael an enemy when he has only ever been loyal to the crown is beyond insane.
And Let's just ignore the insanity that 'I thought he'd be fine as long as I got my happy ending despite the fact that I ruined his life' thought process
Oh, I know, but that only applies to situations in which both rivals are on equal footing; not when you win by ruining the other person's life.
That's why I called him narcissistic because the prince refuses to acknowledge the impact of their actions on Kael and still expects Kael to have unconditional goodwill towards the couple, despite acknowledging how he threw away their friendship (which is why Narcissists are scary because regardless of how much they knowingly hurt someone, they expect to be treated well and act with entitlement.)
Ken x Happiness. TBH I don't like Agia regardless of his background he's horrible to Ken so he better do some serious chasing and character development if he's end game. While white hair isn't really better, I don't think they'll end up together since he seems in love with 'Cain.' No matter how similar Ken and Cain are, I don't think a relationship based on the past will work.