When Ninjas used ninjatos, they could climb rocks unlike other classes. Thus, in theory, while other classes couldn't jump onto the cliff, Ninjas could use their ninjatos to climb on.
The other classes could only sit there and watch, while the Ninjas from the various guilds rushed out, brandishing their ninjatos in preparation to scale the cliff.
But using a ninjato required technique. Although normal players could perform a few tricks, knowing a few tricks wasn't going to be enough to chase a target. What was needed was speed and efficiency. As a result, everyone watched as the Ninjas rushed forward aggressively, climbed for a bit, and then dropped down like dumplings one by one. The number of players who could stay on the cliff could be counted on one hand.