Oni-san no Tokoro e Mairimashita

A lonely girl was driven out of her village as a sacrifice to demons. However, she isn't eaten by the demons— instead she is given a place to live, a futon, and the name "Hinata". "Oni-san" and "Hinata" are supposed to live together as a temporary couple. There are lots of "first times" in their warm and happy newly-married life.

(Source: Amazon, translated)