A tuna walks into a sushi bar and tells the chef "You killed my father!"
Chef says "That's my business, fish."
The tuna thinks this for a moment and says "Very well. Then I challenge you to a game of chess. If I win, you stop being a chef forever."
"And if I win?" asks the chef.
"Then you can feed me to your customers," says the tuna.
So they start to play. Now, tunas love to play chess so in a few moves the tuna has the chef checkmated. "Looks like I win," says the tuna. The chef nods and plunges his knife into the tuna's belly.
"But I won!" says the tuna.
"So did you father," says the chef.