How to become Emperor of China?

[Guomindang]

I'm playing as Japan with the new DLC enabled. I imagine there'd be a casus belli to claim the celestial throne from Ming, but there doesn't seem to be one.

So how does one do it?

[I'm Shinto]

[tonypa]

There should be CB as described in this development diary:

"The Celestial throne is there for any Pagan or Eastern Religion nation to secure for themselves. In practice, The Northern Hordes, the Japanese, the Koreans and the Buddhists are all in with a fair shot at securing the title for themselves and have access to a new Casus Belli: Take Mandate of Heaven"

https://forum.paradoxplaza.com/forum/index.php?threads/eu4-development-diary-28th-of-february-2017.1001995/

[Halala]

I think you have to border the emperor to get CB.

[Guomindang]

You're correct. I figured it out. You need to directly border them; having a "sea-zone border" is not enough