Take me in and I'll love and serve you: Sweet and sexy life with a demi-human girl

Of all the various races, the one with the lowest status is the "demi-humans." Mia lived a meager life with her mother in a small village far from human settlement until one day, they were captured and sold as sex slaves. Trying to at least spare her daughter, Mia's mother gave her a single photo and helped her escape.
One day, Mia turns up at the inn that I run after my father left it to me. In the corner of the ragged photo, the name and location of the inn was written in her father's handwriting. Her mother… was undoubtedly the demi-human woman her father once loved. I decide to take Mia in for a while. She's terribly skinny, and her hair is dirty and tangled. I never wanted anything in return from that girl who had nothing, but… "I… want to be more useful to you… Please allow me to service you tonight…"