Though I'd make my first porst by mentioning Sengoku by Anthony J. Bryant & Mark T. Arsenault. Sengoku is a paper and pencil RPG. The basic main book is very usefull because it is full of Extensive information on Japanese History and Culture, has a huge Bibliography a huge list of Chanbara films wich gives running times, and lots of other great things.
You can get more information at the following 2 sites.
http://www.goldrushgames.com

That's the publisher's web site.
http://www.sengoku.com

That is a specific site just for Gold Rush's Sengoku line. They have a lot of Free PDF files of exerts and maps from the book and the 2 supplemental books plus they have a nice listing of Recomended Books, Films, and CDs too. (The listing isn't as detailed as the one in the Sengoku "core rule" book.)