Transparent Escape Technique

This jutsu has never actually been seen in the series, but allows the user to spy on others without being noticed. Judging by the name, it may make the user appear transparent or invisible to the opponent. It was invented by Jiraiya in his youth to allow him to spy on girls bathing without the risk of being caught. Interestingly enough, the Third Hokage was also interested in this jutsu, prompting Jiraiya to speculate that his sensei was as perverted as he was.