While China's intentions are suspect, I don't understand why Japan has any grounds to protest a Chinese armed coast guard ship near the Senkaku Islands:
For the first time, China has sent an armed Coast Guard vessel near disputed islands in the East China Sea, according to Japan’s Coast Guard. Reuters reports that the Chinese ship, which appeared to be equipped with four gun turrets, sailed within 30 kilometers (18 miles) of part of the Senkaku/Diaoyu island group, which are claimed by both Japan and China.
If the ship isn't within 12 miles, and thus in international waters, why is this an issue for protest?
Of course, I don't understand why we apologized for flying a B-52 close to an artificial island built by China in the South China Sea:
Instead of broadcasting that America will reject China’s claims in the East China and South China Seas, and instead of asserting that American forces will of course operate in international territory, the Pentagon groveled before China, offering apologies. The Journal reports that the B-52 aircrew is being investigated and that the Pentagon is hinting that “bad weather” led the crew to make a mistake. It’s Scapegoating 101.
My understanding is that the zone around an artificial island is measured in yards for purely safety reasons. So we had every right to be there, too, even if accidentally a couple miles from the island.
The difference is, we said we were sorry about that accident while China refused to concede their right to sail.
UPDATE: Now this (older) article says that Chinese vessels entered Japanese waters:
The Japanese government formally protested the entry of an armed Chinese government ship and two other vessels into waters that Japan claims as its own on Saturday, according to an official in the Japanese Ministry of Foreign Affairs. This is the first time that an armed Chinese vessel has intruded into the areas that Japan’s claims as its territory, the official said.
This implies the Chinese got much closer to Japanese territory than that first article claims. Although this very well may be a different incident.