Hell Is Dark with No Flowers, Vol. 1 (light novel) — Yoru Michio

Seiji Tohno sometimes sees the people around him as monsters.

It's a curse that has driven him to a life of despair, living out of net cafés with nowhere to call home...but all that changes one twilit evening when he stumbles across a huge European mansion. There, Seiji meets a bewitchingly beautiful boy dressed in a kimono with a white peony motif on the shoulder who introduces himself as Shiroshi Saijou. This mysterious young man seems to know more about Seiji that he does himself, and before he knows it Seiji has agreed to become Shiroshi's assistant in exchange for room and board. Little does he know however, that this ‘proxy service,' as Shiroshi puts it, is none other than outsourced deathâ€"sending monster-possessed sinners to Hell, that will bring Seiji face-to-face with terrifying new monsters each and every day!