The term "spirit projection " sprang to mind. Are you familiar with it? Japanese folk tales are full of this sort of thing, where the soul temporarily leaves the body and goes off a great distance to take care of some vital task and then returns to reunite with the body. The sort of vengeful spirits that populate The Tale of Genji may be something similar. The notion of the soul not just leaving the body at death but-assuming the will is strong enough -also being able to separate from the body of the living is probably an idea that took root in Japan in ancient times. Of course there's no scientific proof of this, and I hesitate to even raise the idea.