Hell Is Dark with No Flowers, Vol. 1 (manga)

Seiji Tohno sometimes sees the people around him as monsters. Its a curse that has driven him to a life of despairbut all that changes one evening when he stumbles across a bewitchingly beautiful boy in a huge European mansion. The boy introduces himself as Shiroshi Saijou, and before he knows it, Seiji has agreed to become Shiroshis part-time assistant. It turns out that Shiroshis proxy service is to consign yokai-possessed sinners to Hell, which will bring Seiji face-to-face with an unimaginable host of horrors!