There's no chance there won't be a heavy regression back to people be forced into the office. Its never been about productivity, especially in a country where management has much more power than shareholders and where the startup scene is far smaller. Even in western countries the managers, who like everywhere are disproportionately power-tripping self-indulgent psychos, can't stomach it and are trying to wind it back as hard as they can. Its about social hierarchy, domination and control, the status quo, and being a stick in the mud. How can I enjoy wasting my employees time in hours of pointless meetings, and eyeballing and micromanaging them and pushing them around for my own pleasure, if I can't see and control their bodies directly?
The thing I've always been most confused at with Japan though, is that in a country with such a tight labor pool, and with such expensive corporate real estate, how is management able to get away with it? Perhaps someone with better insight than me can explain it.
Either way the best solution remains either running your own shop, or working remotely for foreign companies and/or those run by non-fossils.