The Shirai Ryu are pretending to be worshippers of Raiden, but that's just a cover. They're really spying on the Lin Kuei. So they're close to the Lin Kuei H.Q., in the forrested area near the Shaolin temple.
Ka-Tra

yes, you have to use it in the mission where you defeat scorpion and bring his mask to the Lin Kuei leader at their training camp. I'm sure someone will give you the coordinates as to where to bring the message. The people you bring it to are outside of some yellow huts, and claim to be Raiden worshippers.
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