Spy-nin (mettei shinobi, Literally meaning "spy ninja") are shinobi who leave their villages to go out and gather information to strengthen their villages or even the entire world. They usually act with extreme caution and are sent individually on missions ordered by either the Kage or the leader of an organization. They are usually seen communicating with each and other through code and often use Braille most. Other codes they might use are Chakra Ink, and X-Ray writing which is only seeable with Byakugan or Kagegan. The Strike-up code is a minor code invented by Genno.