The number of princesses that need rescuing is directly proportional to the number of computer games written. Princesses are especially likely to get captured in a martial arts game. The precious king's daughter in this case is called Di-Di and the person sent to rescue her is the ninja.
But it is not enough to just rescue the princess. Before she will go with you, you have to prove that you are worthy by collecting a certain number of idols as you make your way through the Palace of Pearls.
Killing hordes of palace guards apparently isn't good enough these days. The ninja is a pretty mean killing machine though. Apart from the normal flying boots and fists, he can also hack his enemy to bits with his samurai sword and incapacitate him even further by throwing his shuriken (pointed stars) and daggers at him. This is provided that you remember to pick them up as you go along as you forgot to bring any with you such was your rush to rescue Di-Di.
As martial arts games go, Ninja is one of the better ones. The action is fast and furious, most bouts lasting only a matter of seconds, and the excitement level is high - something that cannot be said for many of the clones currently available.
The one annoying feature is in the control menu. The Kempston option does not appear to work, mainly because you have to select cursor joystick instead. Nothing serious once you realise what is going on but surely someone should have picked this up at the game's testing stage?