Mouryou no Nie(2012)

Mouryou no Nie is an adult anime series based on an erotic visual novel. Centuries past, humans defeated monsters in a devastating war and imprisoned them deep within mountains. Three monster hunters—Hayato, Chihiro, and Suzuna—work to contain and eliminate dangerous creatures, though they themselves are monsters seeking peaceful coexistence with humanity. When ancient seals begin to fail and the imprisoned monsters threaten to break free, the trio must journey to the sealed site to prevent catastrophe. The series blends action and fantasy elements as these unlikely protectors race against time to stop a cataclysm that could destroy the fragile peace between their two worlds.