Acceleration of the US missile defense system deployment in Japan is not due to the North Korean crisis, but to the need to resist China, as well as the desire of the United States to create a so-called missile ring along the perimeter of Russia's borders from the West and the East.
Originally it was planned to implement the deployment by 2023, however, as reported by Japanese media, the North Korean crisis forces Tokyo to reduce the deadlines and deploy ABM systems in 2018, while the authorities allocate 2.1 billion yen ($ 18 million) only to prepare for the acquisition of anti-missile systems from the 2018 fiscal year.
Today, Japan has a two-tiered missile defense system. Equipped with Aegis Ashore systems, the ships are armed with SM-3 interceptor missiles capable of hitting a ballistic missile on the middle part of its trajectory. In case of failure, the second level of missile defense will be used - the Patriot PAC-3, whose task is to intercept the missile at the final stage of the flight.
North Korea is only a pretext for accelerated mobilization of Japan. In fact, Japan needs to promptly bring its armed forces to the proper condition to hold China, and to strengthen their positions in the territorial issue over the Kuril Islands with Russia. In addition, Japan needs to be a worthy partner of the United States in the Far East, increasing its influence there.
The fact that Japan began to buy Aegis Ashor from the US, which capable not only to shoot down missiles, but also to launch their ballistic missiles. This indicates the formation of not just a missile defense system, but a system of strategic offensive weapons. This fact causes serious fears on the part of Russia. The fact is that at present one of the priority directions of its foreign policy the Japanese government calls the solution of the issue of transferring the Russian South Kuril Islands Kunashir, Iturup, Shikotan and the Habomai archipelago to Tokyo. The accelerated deployment of American missile defense systems in Japan is perceived by Russia as a threat to its national security and sovereignty over these islands.
Therefore, it is perfectly logical that Russia will take measures to strengthen the defense capability of the southern Kuril Islands. Especially, there is a possibility that Iskander-M missile systems will be transferred to the islands, as well as other advanced weapons of the Russian Federation.
Thus, if Moscow does not show discontent with the strengthening of Japan in the Far East and does not take retaliatory measures - to build up its armed forces in the region, this could affect the balance of power that will be in favor of Tokyo and Washington, which is undesirable for Russia. In addition, approving the deployment of American missile defense systems in their territories, the Japanese government is making its country a potential target for missile strikes by North Korea, China or Russia, thereby creating a serious threat to the civilian population of Japan.