Kimi to Boku no Saigo no Senjou, Aruiwa Sekai ga Hajimaru Seisen S01

For many years, a great war has been going on between the scientifically advanced empire of Nebulis, the land of witches, and until the youngest knight who has taken the title of the strongest warrior in the empire meets the princess of the rival country. Although they are sworn enemies, the knight is impressed by the beauty and dignity of the princess, and the princess is also impressed by the power and way of life of the knight. Will the war between them ever come to an end?