How Japanese black companies oppress workers (2014)

Interestingly, this is actually possible under Japanese law/legal precedent. If an employee, for example, decides to put in notice and then half-ass their job until their departure date, a company could actually sue the employee and win.

Other Japan-labor-law fun fact: if you are a contract worker, it is literally illegal for you to quit prior to your contract expiry date. Hope you like that job you signed onto!

Obligatory disclaimer: IANAL

Having seen the perverse incentives this creates and the various ways in which it can be abused, I have come to the conclusion that the American “at-will” employment model is actually a good thing and benefits workers. No one should discount the value of having the power to tell your employer to fuck off at a moment’s notice with no practical repercussions. No one should be required to stay in an abusive relationship a moment longer than they wish to.

I think you are confusing "it is possible" with "it is common". Never heard of people in Japan get sued for quitting, even with shady English teaching centers. But definitely seen companies do them for scare tactics though.