This is new for Japan:
With its official operational date fast approaching, Japan’s first Amphibious Rapid Deployment Brigade kicked off the bilateral Iron Fist 2018 exercise on Friday with an opening ceremony alongside its Marine Corps hosts. It wasn’t a time for long speeches. ...
Exercise scenarios, as developed by planners to support the force’s training objectives, include taking back a contested island and reinforcing it with additional forces, officials said. “It is designed very similar to the stuff we normally do,” Fridriksson told reporters after the ceremony. “We are just trying to improve the Japanese amphibious capabilities… Island defense can be one of them.”
The Senkaku Islands to the southwest of Japan that China claims as their own is not mentioned in the article but this is the focus.
Personally I think that it is nonsense that Japan's plan is essentially to count on racing in ahead of a Chinese invasion force.
Because China as the potential aggressor (because Japan has them now this is a basic fact and not even a judgment on who should own the islands), China can strike while weather or other factors hinder Japan's ability to race China to the islands.
So Japan should assume they lose the race. Lose the race to a nuclear power.
Japan administers those islands and America says they fall under our defense pact with Japan. Japan should fortify those islands.
And if putting troops there seems too provocative (or impractical from the small size), send in the robots.
If not, one day China will use the island building skills they are honing in the South China Sea to turn Japan's islands into forward outposts.