I don't know much about Sinon. I have never run a game there - although I played some Oriental Adventures years ago …

We know that …

• Way and Shan (deities, temple of the Shrines) came from Sinon (It is in their backstories)
• The Shay dynasty of Porters bar came from Sinon - generations ago

But I think that is about it for established in-world Lore.

• Monk
• Samurai (and Ronin archetype)
• Ninja

There is clearly a system or Higher ranks. At the moment I just need two of the lowest, who might be leading a colonization attempt, these come from Chinese and Japanese traditions and are not used in quite the same way as they were then. Not a system for the purists, but one that works well with the rules, does what I need and is intelligible to players.