In Japan, there's a really symbiotic relationship between unions and corporations. Unions are very powerful, but they also take stakes in the corporations. I'm pretty sure that union reps often sit on corporate boards. Japan has a long culture of employee relations, but they also work their asses off. I don't think Japanese unions would cover slackers, which is a popular view of US unions.
popular =/= accurate. But yes, the most criticized aspect of unions (at least from a liberal lens) comes from its ability to rally around every worker in the union, regardless of individual productivity.
But historically, unions in the US neeeded those protections because it's way too easy to fire a US employee for anything that's not illegal. Japan doesn't make termination any easier, it's just incoporated at the government level instead of corporate. To compensate, Japanese "slackers" just get good severance packages as an incentive to get out, or even move them as far out of the picture as possible.