Kitsunemori, a D20 sourcebook by Dog Soul Publishing. 

My personal favorite setting. It focuses on a rather small area, populated by human and kitsune. It includes conversions of the core classes to a feudal Japanese setting, as well as a new class, and of course kitsune as a player race. There is quite a bit of focus, and game mechanics, on prestige and court politics. Both amongst kitsune, with tricks being a way to build your renown, and the human courts.