Title: Ari An no o shiri
Harem/Romance/Action
Context: Nazi Germany wins WWII, and begins a campaign of world conquest that leads to their world conquest.
MC is Hans Rupershuto, a German American in California. He gets transferred from Adolf Hitler Academy to a new school, called "Lebensborn High School."
Since he's a harem protag he's not going to want to do that. The Principle grabs him and says: "This is not for yourself, this is for your Fuhrer. Now go to Lebensborn High and FUCK!"
MC arrives to the high school, and sees that its essentially full of females. He doesn't know how he can repopulate the conquered territories with children so much, but the Reich has given him free access to shittons of women.
He goes on the usual antics of a Harem, only to find that his childhood friend is also there. She is shocked to see him, and he's shocked to see her.
Eventually, with a plethora of sexy women throwing themselves to him, he gets stressed from their constant infighting, to the point where the school degrades into civil war.
One side, commandeered by a blonde Tsundere, demands that they get him for sex slavery. They think he should not have any freedom because he's repopulating the world. The Blond tsundere eventually gets very tyrannical.
The other side is more "humanitarian", they see him as more of a figurehead to represent their highschool to the government. This is led by a waifu level black haired yandere who loves the MC, and also the childhood friend is part of it.
Violence gets so bad that childhood friend gets injured, MC grows some balls and stops fighting. The government and Principle, who allowed this to happen. Finally intervene and transport MC out with his childhood friend.
MC returns back to normal life, and they kiss. You know, romance stuff.