Ninja: Japanese or Chinese?

That was Fish's recent question while I was driving. Now we guessed Japanese, but were confused because we are aware of many chinese martial arts so we decided to check the internet later. Naturally the microcassette recorder that we bought for just such a purpose was not in the car again, so it is just as well I remembered it later.

Oh - our guess was correct, and the boys were amused by some of the things we found along the way, such as Ninja vs. Killer Tomato