From The Asahi Shimbun: “The area where the trespassing submarine was first sighted has strategic military and economic significance for China, military experts say.
Defense Agency sources said submarines from various countries often crisscross the waters between the southern tip of Kyushu and the Okinawa islands.
But experts say China would have a strong motive for keeping a submarine in that area.
The waters are vitally important to China, especially if relations should deteriorate with Taiwan. ”
The full article is here.