Orcsen Oukokushi: Yaban na Orc no Kuni wa, Ikani Shite Heiwa na Elf no Kuni wo Yakiharau ni Itatta ka

Gone are the days of swordsmanship and chivalry. Now is the age of gunpowder and war. Our story has two players. The first is Orcsen, a unified nation with many demonic races, led by the oft-reviled orcs. And the second is Elfind, the kingdom ruled by the beautiful yet vainglorious elves. Dineru, chieftain of the dark elves, has been forced to flee her homeland from enemies she had once trusted as friends. In the midst of their forced diaspora, she has a fated encounter with the leader of Orcsen, the orc king Gustav... (Source: MangaDex)