Anyway, once you've passed the karaoke challenge, everyone in the bar will start punching you. If you survive the beating (that is, kill everyone), an old man will hand you a blank piece of paper that needs to be exposed to sunlight for an hour if you want a map to appear. And then you have to do exactly that: choose the "expose to sunlight" option and wait exactly one hour without touching the controller. If you so much as press a button during that hour, you have to do the karaoke challenge again.
A testament to how much the game hates you: It's pretty much the only thing in the game you can't punch.
The map, it turns out, shows directions to a treasure island in the Pacific, so naturally you have to take hang gliding lessons and fly there yourself while UFOs shoot at you. Assuming you can master the sadistic hand gliding controls (it's extremely easy to crash into the ocean), reach the island, find the treasure and complete the game, you will be rewarded by ... a black screen with Kitano's face and the words "The end."
We take it back -- this may be the greatest thing in the history of video games.