I assume that you are asking about the samurai, who were the class of Japanese warriors similar to the knights of medieval Europe.
If this is the type of Japanese warrior you are asking about, the most important thing that they wore in battle was full suits of armor. This armor could be made from leather or from iron. These suits of armor covered the samurai from head to toe.
The major parts of the armor included a helmet, breast plates, shoulder protection, long glove or sleeve like armor to protect the arm, thigh and shin guards. Follow the link below for a much more detailed discussion of samurai armor with illustrations.
sorry, what i meant was whatdid japanese warriors wear.