Kimi to Boku no Saigo no Senjō, Aruiwa Sekai ga Hajimaru Seisen

Kimi to Boku no Saigo no Senjou, Aruiwa Sekai ga Hajimaru Seisen (キミと僕の最後の戦場、あるいは世界が始まる聖戦, lit. "The Last Battlefield Between You and I, or Perhaps the Beginning of the World's Holy War") aka Our Last Crusade or the Rise of a New World is a light novel series by Kei Sazane with illustrations by Ai Nekonabe.

Plot
The Empire endowed with an advanced level of knowledge, and the Nebulis Imperial Household Agency feared as the 'Country of Witches.' On the long-lasting battlefield between these two countries, a boy and girl met.

The ice witch princess praised as the strongest in all of the Imperial Household Agency―Aliceliese.

The swordsman who became the ultimate force on the battlefield at the youngest age throughout all the Empire's history―Iska.

"If you capture me, your dream may also be fulfilled." "Likewise, if you defeat me, it will become a step in the unification of your world."

The two arch enemies were to kill each other. However, the boy had his heart stolen by the girl's beauty and nobility. And the girl was attracted to the boy's strength and way of living. Even if walking alongside one another would not be permitted and the only path before them was to defeat each other.