A real thing that has been so stereotyped by TV that now people think its fake. It is a person who trains in the art of ninjutsu (an art in the bujinkan) otherwise known as budo, the current grand master is Masaaki Hatsumi, who lives in japan.
Person who actually trains in an ancient japanese martial art: "I'm a ninja."
Ignorant person: *Does karate kid pose mockingly*