Kare to Hitokui no Nichijou

Kare to Hitokui no Nichijou (彼と人喰いの日常, lit. "Ordinary Days with a Man-Eater") is a light novel series by Neko Kamisaka with illustrations by Ayumu Kasuga.

Plot
In order to save his life, Tooya made a pact with an ancient demon. The price is that he has to pick a person for the demon to eat every month.