The Time River has many peculiarities, such as it being measured by time rather than length, the lack of human race, the inability of the Brahma Tower, which controls the path of space, to be transported to the world within the Time River, and so forth.
"Only those who enter the Time River at the same time can see each other, like you and Ji Kongkong."
"People from the past can't see those from the future, and the future can't see the past either. These are the restrictions placed by the Time River on outsiders. Of course, you could not possibly see me."
"Creatures of the Time River are not bounded by this rule. For instance, Ancestor Shun can see you now, as well as your future self."
These rules that Ji Zhi shared were not discovered by him, but recorded in the scripts left by Emperor Shun, supplemented by conclusions drawn from the attempts of generations of the Ji family.