Apocalypse Bringer Mynoghra, Vol. 3 (manga): World Conquest Begins with the Civilization of Ruin — Fehu Kazuno

Takuto has successfully brokered an alliance between Mynoghra and the neighboring nation of Phon'Kaven-- who've settled the city of Dragontan atop a vital strategic resource known as a “Dragonvein Grotto”. His next move is to send a research party. After much deliberation, Takuto elects to send the twins Cary and Maria, along with a suspicious looking medic. How will they fare on the evil nation of Mynoghra's first mission...?