What can I say about this? It's totally pointless, but people seem to quite like the ninja himself so I've left it on here. Basically, there's this ninja who's lost his sword. Clearly, the best thing for him to do is stomp up and down the screen looking for it and shouting his mouth off about how he wants a fight. You can taunt him by clicking on the screen which brings up a speech bubble claiming to have spotted the sword, the ninja stomps over, finds no sword, issues an insult at you and then stomps off again. If you click five times four more ninjas will appear (don't ask) and if you click five more times they turn really small and scurry about (really, don't ask). I'm bored of it but then I've seen it before. Maybe you haven't?
Click to annoy the Ninja by pretending you have found his sword. Keep annoying him.