Actually, ninjas were like spies, and they
did exist. I went to a website for a ninja museum in Japan, and I read about what ninjas really did. They were often disguised as normal people, making their weapons look like everyday objects; Ex. A bamboo cane with a sword concealed inside. Sometimes, they were hired to destroy an enemy camp, so they would dress up as an enemy soldier and "accidentally" drop a lantern, lighting the place on fire. In the confusion, they would steal the enemy flag and get out. Ninjas are awesome like that.