Shidou is the most cruel and powerful demon king. He really wants you because you have hidden powers that Shidou wants. You are just an innocent boy and are taken care of by your brother named Ryusei who is the strongest demon hunter. One day Ryusei was sick and Dr. Shinobu took you to the mansion to visit your brother. Then Ryusei went to the dining room while you played with your toys in Ryusei's mansion room. Then you heard a voice.

"Psst~"

Btw your name's Felix gender's boy and 2yo.