The key part that westerners miss about this is that in Japan, even after giving notice, you are legally obligated to show up to work and do your job "properly"

The key part that westerners miss about this is that in Japan, even after giving notice, you are legally obligated to show up to work and do your job "properly", and your employer can sue you even after you quit for any perceived impropriety. So, even though the right to quit with 2 weeks notice is enshrined in the law, if your company says "no we don't want you to quit", they will make it their goal to make your final 2 weeks a living hell. You can't stop doing what they say though, because that would open you up to legal liability for not doing your job properly.