User blog comment:Crimson Marauder/Vampires and Demons/@comment-25942629-20161010163645

The humans knew little about vampires at the beginning of all this, so it's not surprising they wouldn't know of such an effective way to create a demon.

Ashera's heart may be missing, but so is his body. He now resides within a sword and Yuichiro's body as Asuramaru. Does he even have a body? Did it become ash after he was imprisoned within the weapon? If a demon is something like a soul, then maybe the demonic soul was extracted and put into the Cursed Gear. The body would be left empty. If it's like that, then the body could have been abandoned somewhere. More likely, since Ashera was a vampire, the body was put into the sunlight and burned to ashes. After all, with the soul/mind removed, there would be no need for the body.

Of course, this is all only a theory since we know even less about demons than we know about vampires.