Seikon no Aria, Episode 1

In a continent where the power of succubi is strong, a terrifying plague known as the "Lust Demon Disease" runs rampant. When people suppress their sexual desires for too long, they become violent, attack others, and ultimately transform into monsters. Aria, an "Exorcist Sister" blessed with the proof of God's protection—the "Stigma"—uses her holy power to save the infected who have turned into demons. Ah, ahhn... this sacred act (S○X) is... of course, all for the purpose of eradicating the Lust Demon Disease!