Legend of the Five Rings RPG - Emerald Empire: The Essential Guide to Rokugan - Rules of Play says:

Emerald Empire: Fourth Edition is a comprehensive guide to Rokugan that will bring the world of Legend of the Five Rings alive like no other book. Emerald Empire mixes detailed written descriptions of various aspects of Rokugani life, from politics and war to commerce and the basic rhythms and rituals of daily existence. The book also has handy reference material for those who wish to know everything from who answers to whom in the bureaucracy of the Imperial Court to strange and exotic visitors from foreign lands.