Whose soul in shinobu body? Im confused

It is the soul of a random young boy that Takashi's grandfather found. The boy is never named specifically, but I'd assume his name was Shinobu. Since the boy was the same age as Takashi, he was thought to be a good sacrifice for Takashi's doll. Maybe he was in an orphanage or perhaps living on the streets when Takashi's grandfather found him. The boy's body would have died many years ago when his soul was transferred into the doll that is now known as Shinobu.