Yoroi Shitagi or Gusoku Shitagi is a layered under shirt or jacket worn by samurai, under their armor during feudal Japan. The yoroi shitagi is a kimono style shirt that ties closed just below the throat and has a thin obi (belt) attached at the back of the waist. The samurai would ceremonially dawn their shitagi by inserting the left hand first, followed by the right. The neck would then be tied and finally the attached obi tied from the back to the front. There are several styles of this “under armor” shirt. One of the most common styles was typically made using linen on one side with silk on the other. In some shitagi one have linen or silk on both side and/or could be reversible. This makes for a more comfortable feel with easy care and cleaning on the outside. The layers of materials also provides extra protection as it acts as a form of gambeson (arming coat) which helps protect from chafing of the armor and can help resist or stop any edged weapon that finds its way past the steel plated armor. This has proven to be an essential part of the armor and was the second clothing item added, after the fundoshi (loincloth).
Iron Mountain Armory has reproduced this gusoku shitagi using traditional design patterns and has made our shitagi reversible. So you can wear it silk side in, to protect the art silk while wearing armor and once the armor comes off, you can reverse the shitagi to show the art silk pattern on the reversed side.