Kuro no Senki: Isekai Teni shita Boku ga Saikyou nano wa Bed no Ue dake no you desu

Kurono Crawford, a noble of Cepheus Empire had a secret. It was that he came from a different world... modern Japan. Having the knowledge about the modern weapons and his sense of values, he was an existence almost like a cheat, aiming to be the Harem king. Abandoned by his superiors, left in command of the Empire's rejects consisting of demi-humans such as Minotaur's, Dwarfs, and Elves, and thrust into a position as head of a poor fiefdom, Kurono will do everything he can to rebuild and strengthen his forces and revitalize the land, aided in part by his knowledge of the other world.

(Source: Novel Updates)