Ninja was pretty unique person.
They sneaked into an enemy as spay and assassinated.
They didn't fight squarely with an enemy.
They are said that we could run on the water and use fire with freedom, but we are not sure...
In Japan, people made many anime which is related to Ninja.
By the way, Today is called "Ninja's Day".
February 22th→2.22→ニンニンニン lol