She's the Strongest Bride, But I'm Stronger in Night Battles: A Harem Chronicle of Advancing Through Cunning Tactics (Manga) Vol. 1

In this Mature-rated isekai manga, an ordinary man becomes a military genius and the hottest lover in the realm—in another world!

Compelled to marry a royal demoness and put to work—on the battlefield, and in her bedroom—Albert finds his new life in another world anything but peaceful. Yet thanks to his knowledge of Earth’s history, Albert is able to launch a revolution, and is having a ball doing it alongside his sexy demon bride!