A long time ago, but not really that long ago, in a galaxy far far away, but still somehow our galaxy...

There was a man known as Lee Minhyuk.  He was trained from birth to be an incredibly deadly monster slayer.  He traveled all over the country with his younger partner Yook Sungjae, and the two of them killed monsters, and saved lives everywhere they went.  Minhyuk had always known that he had a gift for slaying, but he never knew why...  

Little did he know that the truth behind his "gift" was about to make him the target of the most powerful and feared demons in the Underworld... The Demonic Trinity.  

Now we begin to read from the diary of Lee Minhyuk...