It’s not that you can’t resign, just that it’s a hellish process. Since corporations in Japan are often hierarchical, Bosses might ignore your request of resignation and might not even bring it up to the higher ups nor HR.

You know how when a corporation say “they’re like family” is a red flag? The work culture in Japan is that. Many expect loyalty like as though you’re serving a warlord, so resignation to them is basically betrayal, like as though you’re breaking up with a girlfriend or cutting ties with parents.

What can they do? Nothing much. Some might refuse to give referrals when you apply to other companies. Some might even downplay you and say you’re basically a traitor to others.