Mc Isekai as the hero.
Kill the demon King.
Get betrayed by human.
Destroy human kingdom.
Run away with a demon queen.
Why do I feel that MC’s mind is like that of a middle schooler more than a war veteran. Muh, I hate the world and everyone, only my beautiful demon queen wife is my ally
What is this ? A kid ?
P/S: I don't think he did anything wrong with destroyed the kingdom that forced him to fight or didn't accept the princess's request. I just find his mental monologues too cringe and childish for my taste here.