I would say more Korea and China than Japan, in terms of what Asian flavour should dominate. Cyberpunk originated when Japan was outpacing the west in terms of heavy industry, but it's really poorly adapted since then. The Japanese economy now is in a rut due to their inability by and large to adapt to the digital revolution, meaning China and South Korea have outpaced them via cheaper labor and exports. Now Japan's the 'poor man' of the developed world, in a recession for decades and with a dwindling population, it would be kind of anachronistic to have them be the mega power.
But then, I live in Incheon so I might be biased. That said, I'm definitely interested in an Asian focus to this.