If he disappears, who killed his grandmother? If he doesn't disappear, where did he come from? During this period, even his parents hadn't been born yet, so that person's actions wouldn't be recognized by the cosmic rules.
In order to eliminate the possibility of a paradox, the macro laws of the universe do not allow time to flow backward.
But speaking of time, it could also be a term imposed by humans. Feng Yi learned from Mo Ying's narration that time does not exist in a real sense. Birth, aging, illness, and death, as well as the destruction of galaxies, are merely cyclical processes generated by the workings of gravity, belonging to a type of calculation formula. Their worldview certainly never lacks the concept of time, but this is merely a spatial axis, tangible and visible.
