"Zi Zi" says: "The four directions above and below are called the universe, and the past and present are called the universe."
For Song Yi, if the thing between him and Song Ling is "yu", he will meet gods and kill gods, meet Buddhas and kill Buddhas, and the end of the world will be just around the corner.
However, there is a "space" between them. Even if they are close to each other, it is the end of the world, let alone a thousand years.