I have described the characteristics of dreams so far. You dream of the world of the future. The self in the dream world is yourself or someone else. The past self or others dream of you now.
 
So do you dream of your afterlife?
To prove the afterlife with a dream, find out if the dream self is a spirit.
 
Do you dream of the spirit world?
The radio technology has developed in Japanese underground society. You remember your dream self. At that time, you emit radio waves to the part of your brain that recognizes the image and detect the reflected radio waves. That is the frequency of the dream self.
 
Check if it contains spiritual frequencies. How to get a frequency of a spirit? It is here. Ask your Japanese friend for details.
 
If the dream self is a spirit, it is a dream of an afterlife. If it is not a spirit, it is a dream of the human world. Find out the dreams of those who will die soon.
 
I think people do not dream of spirits. I don't think the dream body can be put into the spirit. But what about the reality? It becomes clear when you research it.
 
Summary
To prove that you dreamed of the spiritual world, find research if your dream self is a spirit. Examining near-death experiences will settle the controversy.