The 19th Century Neoreactionaries Who Won

The Meiji "restoration" wasn't really a restoration to a history that existed.

Some guys into Shinto history and Dutch methods made the idea real.

So Japan didn't really get Imperial succession laws until 1889.

Before that, succession went through coalitional power expressed in ritualistic norms.

In the 14th century, for examples, it was argued that the Emperor was whoever held the Imperial mirror, jewel, and sword, and had unbroken descent from the sun goddess Amaterasu.

Imperial succession was based on the meme.