We're not just human we're soul.

I know even you atheists feel that thing that is you that is so separate from other things i guess. what is it?

I recently met a person whom feels he has had a walk-in.
It has been 11 years now. His human soul was replaced by two demons.
He could be lieing but I see no motive.

Are all walk-ins fake, or are some real?
What are the odds that it is 100% false?