Monster Hunting Guide

When I was 3 years old, I lost my parents because of demons. At the age of 22, in order to avenge my parents and protect more lives threatened by monsters, I opened a studio called Hunting, which existed only to kill monsters. I never thought that one day I would fall in love with a vampire, and I never thought that Dragon Calm, the demon ancestor that has existed since ancient times, would live in my home, and I never thought that one day I would fight against humans side by side with the five demon ancestors. Who is the murderer of my parents? Should there be demons in this world?