You might be interested in past posts from the FAQ section on this topic:

• Is it true that there were no shields in Japan during the Samurai and in that case why?
  ^(11 Jan 2013 | 11 comments)
  ^(/u/AsiaExpert details how shields did not fit into both smaller scale and larger scale Japanese warfare in different time periods.)

• Why aren't shields prevalent in Feudal Japanese armies?
  ^(05 Sep 2015 | 4 comments)
  ^(/u/bigbluepanda analyzes and illustrates various Japanese weapons and how they didn't work well in combination with hand shields.)

• Why were shields so much more prevalent in warfare in Western Eurasia, Africa, and some parts of the Americas than in Chinese and Japanese warfare?
  ^(27 Jun 2012 | 70 comments)
  ^(/u/Abiding_Lebowski describes Japanese use of hand shields.)

You can ask followup questions by posting your questions in the comments with experts tagged to direct questions to them.