DEMON: Three of me

A 18 year old young man dies in car accident and goes through the wheel of reincarnation, he reincarnates in one of the three million universes as a five year old demon.
of course he doesn't retain his memories because of the rules set up by all gods.
on the day of his birthday the demon empire his attacked by the humans on their own continent to wipe them out. when our protagonist is escaping through a damaged portal he is sent to the human continent on the other side of the world by accident, he ends up falling in a large cave and lands on a pure soul stone head first where he loses conscious.