The boats didn't cross into Japanese territorial waters but the vessels were in Japan's "contiguous zone," according to Japan's Kyodo News Agency.
Thee pursuit, if not interrupted, may be continued outside the territorial sea or the contiguous zone until the ship pursued enters the territorial sea of its own country or of a third State.
In the South China sea, China has internal waters, territorial sea, contiguous zone, exclusive economic zone and continental shelf, based on the South China sea Islands.
The breadth of the contiguous zone is twelve nautical miles.