According to Reuters, Japan intends to express concern to Beijing with the approach of the Chinese military ship to the territorial waters near the Senkaku Islands. In China they are called Diaoyudao Islands and considered to be Chinese territory.
The Ministry of Foreign Affairs reported that the Deputy Minister Akitaka Saiki summoned the Chinese ambassador in Tokyo to "express serious concern" over the incident. The Chinese naval vessels are often spotted this area of the East China Sea, but this time the ship had gone too far.
The Japanese Foreign Ministry also reported that at about this same time, three Russian military ship were in the same area near the alleged territorial waters of Japan.
The Ministry of Foreign Affairs investigates whether the actions of Beijing and Moscow were cooperative. It was found that none of the vessels crossed the boundaries of Japan's territorial waters.