Royal fighter

A story about young boy and girl. A girl who forgot everything woke up in a house with three bodies covered with blood, the was a monster and the only thing that the girl was saying is a name, when the girl was acctack by a monster, someone came and save her. The boy's name, was the name that the girl was saying. What is this all about? What happened to the girl and the boy before they forgot how they get to the house? A story full of mystery and fight the demons.