Astarte's Knight

From 9ethtranslations:

My life of being continually abused by my parents ended when I was 18.

The next time I opened my eyes, what awaited me was my life as the lowest class of demon “Ghoul”, protecting one of hell’s castles, Astarte Castle.
The lowest class of demon, "Ghoul”, was my new life.
I was scorned by the demons in the castles for being such a weak, low ranked monster.
But my fate was changed when I met the castle lord’s daughter, Astarte (age 10).

Japanese Web Novel