Apocalypse Bringer Mynoghra, Vol. 3 (manga)

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…?