This is not a systematized form of magic, but rather a collection of personal accounts shared on platforms like online forums. It's a genre of stories that have been created, with many people posting accounts of experiences like traveling to a parallel world, or, as a variation of that, to the past or future. Therefore, it likely contains a lot of pure fiction, and can be said to be less reproducible than magic, even within the same occult field.
While no definitive method has been established, the most common explanation is that one’s soul or consciousness—having departed from the current physical body via a lucid dream or an out-of-body experience (it is unclear if this is the same concept as "astral projection")—becomes linked to a body in a parallel world instead of the one in this world.
However, this is not the only explanation offered; some accounts describe shifts occurring without any warning, while others claim that the individual found themselves in a different world after an event such as being struck by a vehicle.
I just looked it up, and it seems there are similar concepts on Reddit called "reality shifting" and "Timeline Jumping," so you might want to look into those instead.
If you are searching in Japanese—perhaps using translation tools—you can try looking up the term "Parallel Shift"
I am looking for perspectives to come to my won conclusion and would love to hear yours
