Yagate Boku wa Daigunshi to Yobarerurashii

This is a heroic fantasy story of a great military strategist who has been branded incompetent.

In a time period where humans fight with guns and modern weapons, the fantasy tribes have been destroyed by their overwhelming power-- A human boy raised in a elven village - Gardy - broke the village's law and has been exiled. Thus he went to the Intrasia territory which is governed by the gold princess Florin.

(Source: MF Bunko J)