re: realistic or not, as the MC remarks: the world is a "light-hearted otome game" so the setting isn't meant to be that detailed. Also lest anyone forget, the world has 'artifacts' from a technological age, and magic. Once you throw magic into the equation, all bets are off regarding what's realistic or not.
Honestly how could that demi-human beat the mc? Isn't he supposed to be ultra strong or something like that? And is Marie his sister? Hope he kills her, disgusting bitch.
Yup that is exactly how I feel with harems (and reverse harems). It is suuuuuper unrealistic and boring to have a guy or girl have everyone fall in love with them.