Guess it's time we (those of us on FR who don't know) started learning more about Japan's forces and capabilities...
Instead, the Coast Guard is part of the Ministry of Land, Infrastructure, and Transportation (MLIT). Here's a summary pdf from MLIT's website. (Give it a minute, it seems to load very slowly on my machine.)
The JDA website in English (sorry, it's always very, very slow.)
The MLIT's website in English.
For what it is worth, the Japanese Coast Guard also sank a North Korean spy ship a few years ago.
The JMSA (Japan Maritime Safety Agency, aka Japan Coast Guard) is a civilian maritime law-enforcement and rescue agency, not a military organization.
(Our United States Coast Guard is likewise an arm of the Department of Homeland Security, not a military force. In time of war, the Coast Guard assumes the status of a military force and its administration is transferred to the Department of Defense.)
It's important to note that strictly speaking Japan has no military forces of any kind. Under Article 9 of the Japanese constitution (which we wrote), military forces are forbidden to Japan forever. Such armed forces are may be maintained (Japan has four) are by law "police agencies", and may only be employed for law enforcement, including the protection of the nation's legal boundaries. Thus all Japanese armed forces are de jure "homeland security" forces, and all armed forces members are de jure civilians -- employees of the Japanese civil service -- not sworn soldiers.