Jack really did not like anime. That ten seconds spent watching Naruto on TV all those years ago had mentally scarred him, and physically scarred his television (It now has a small crack on the glass where Jack had thrown a remote at it).
So, it's quite understandable that he did not like the people who created anime. It is slightly less understandable that he hated the race of the people who created anime, but there you are.
The fact that the ninjas mentioned Naruto just fanned the flames.
Where were we? Oh, yes.
"AAAAAAAAARRRRRRRGGGGGGHHHH!" Jack screamed. The ninjas recoiled at the sheer force of anger in his voice. When they could see clearly again, what they saw was even scarier.
Jack was running straight at them. He jumped and soared gracefully towards the ninjas. Well, it was pretty graceful until he kicked at one of the ninja's heads. Needless to say, that ninja probably died.
The other four had drawn their swords again, and could actually have struck Jack, had he not punched one of the ninjas in the face and grabbed his sword. Three ninjas to go now.
One of them tried an overhead chop, but Jack sidestepped and kicked at the ninja's leg. Then he swung his own sword and cut a deep gash into the ninja's arm. The ninja clutched his arm and fainted.
Jack threw his sword at another ninja. It went straight through his heart, killing him.
The last one charged at him, but Jack grabbed his arm and twisted. He heard a crack. The ninja dropped his sword and howled in pain. He kept on howling until Jack slapped him in the face, knocking him unconscious.
"Wow, nearly a whole chapter of me beating up ninjas," Jack said calmly, pulling his new sword out of the ninja's body. "And almost no jokes at all," he added.