Samurai Knight Fever is a set of free wargames rules for Japan’s Age of Battles: 1550-1615. The author is Tod Kershner, who is the designer of popular and established wargames rules including Warfare in the Age of Reason, Age of Discovery, Age of Napoleon, Pig Wars, A Firebell in the Night and Iroquois Terror.
Kershner is a friend of mine, and I have long enjoyed playing in his games.