Japan already feels the present of the South Korean eating away their market share in electronic gadgets, automobiles, shipbuilding, and a bunch of other industrial products and services that in the past could only be produced and provided by Japan.
For a country with no natural resources Japan will face more economic decline in the future than it already is. It used to be that Japan was one of a very few countries that could produce industrial products like cars, ships, electronic gadgets, machineries etc but now as the world progresses, more and more countries can start producing these industrial products. As a result, more countries that used to buy from Japan will stop or reduce their buys and even compete against Japan.
With no natural resources and losing the international market share to their new competitors, Japan's income per capita will reduce inevitably. Just a fact that anyone can produce their own brand of cars, ships, or electronic gadgets is already contributing to the decline of Japan since they no longer need to import from Japan.
The South Korean not only can produce their own brands of industrial products but also snatch away a chunk of the market share that the Japanese used to own the whole "pie" despite the inferior qualities of the South Korean's products vs Japan's. I would say that the South Korean's rise in industrial development is one of the major contributing factors to the decline of Japan's economy so don't be surprised if Japan is behaving like that.
