This sounds like a bit of a health hazard, doesn't it? Think about it...
People will want to get high scores and whatnot on that thing. They'll want their milk-spraying champion to reign supreme in every urinal in the city. They'll want to raise the girl's dress so high that some underboob is made visible. And how do you do all that? By peeing more. And by that, I don't mean "more often", I mean more.
People will be consuming huge amounts of liquids and holding it in or as long as they can, just so they can do better at a pissing minigame. There will be a whole demographic of Japanese men with loose bladders and kidney problems...
...and then someone will decide to make porn to cater to those people...