Japan would never ever let another foreign Asian country take them over. Japan is still a very nationalist country sinceWWII and its been steadily increasing. If they didn't have a population issue, their work conditions were better for the everyday person, and companies were not allowed to run rampant with corruption, they'd probably be in a similar position at the turn of the 20th century of being an Imperial country again looking to dominate all of Asia.

We're already seeing an uptick in national military fervor take place in Japan with their multi-billion dollar increase in their defense budget because of threats like North Korea and Russia. The US will happily arm them too and look to them to be a strong ally as tensions rise in the Pacific. Japan will probably be a sleeping beast in the Pacific that no one should fuck with in the future, earthquakes or not.

My prediction with the future of Japan is that we will probably see the eradication of their defense force in favor of starting a Japanese military and navy again. This will be highly controversial as the rest of Asia will not be thrilled by this and many would argue this would only increase tension in the region. They will probably mostly buy surplus from the US, but I also wouldn't be surprised that we see new state of the art aircraft from Mitsubishi and Toyota (Mitsubishi already has plans to develop a new fighter). The biggest controversy will be that they will have nuclear arms, but as tensions keep increasing, most will see that as self defense against North Korea.