It's just like being a real ninja! Only without all the sneaking, killing and presumably the fun that would ensue
You start off in the forest surrounding the castle. Some enemy Ninjas appear- lovingly rendered by an orangutan in Microsoft Paint. Using your Fire button, you can throw ninja stars at the enemies. They'll throw ninja stars back. The thing is the enemy Ninjas come in hordes of five or six, but your stars only come in bursts on three. So you frantically throw three stars, hitting two Ninjas and missing the others. Then you panic and run away. It's here that another problem becomes apparent- the enemy Ninjas run just as fast as you.
This isn't to say that The Ninja is impossible- rather, it's so shockingly difficult than even the word "impossible" fails to come to terms with how frustrating this game is. If you manage to overcome the rampaging hordes of Ninjas, you'll face a boss-type character. He throws some sort of projectile at you. Then you die. I assume this is a boss, of course, because by that stage I'd turned off the Master System in digust, my ears still ringing from the "soundtrack" and my eyes still bleeding from the "graphics".
Maybe I've just been playing too much Ninja Gaiden on the Xbox lately. Maybe The Ninja really is that bad. Either way, as a piece of software, The Ninja is completely redundant. I plugged it into the Master System expecting Shinobi- well, this is Shi... possibly the worst Ninja-related title I've ever played. I'd tell you to avoid playing it at all costs, but you really should have worked that one out by now.