Shinoda was the keeper of nightmares. The demons he used to create nightmares were kept where a normal animal's organs would be.
One night, during his job, a child had woken up as a demon was being passed through him. In the nightmare realm, this is considered the fault of the demon's master.
The demon was tracked to Shinoda, and the keeper was whisked away to "be taken care of." The Arthex was sentenced by the nightmare realm's overlord to beheadedment, but the keeper managed to free himself as the saw was lowering, but not quite in time. He survived, but his lower right leg was chopped off.
The overlord was not informed of Shinoda's survival, but his son knew. The overlord's son managed to catch Shin before he escaped into the human world. As the two were very close friends, the nightmare realm's prince sewed Shin's mouth shut as to stop demons from escaping.
The demons occasionally attempt to corrupt Shinoda's mind and take over his body, turning the keeper into a demonic form.

oMF, HE IS MY DANLER CHILD-

i CAN FEEL THE DAN-NESS RADIATING FROM HIM-

Is it bad that I find him adorable?
Also, awesome backstory!

cute c: