Looking at a map that looks like Japanese waters to me.
Although I also know there is a huge US military presence on Okinawa. Did the US forces notice this fleet? Did it not share that with Japan?
Barack has certainly emboldened our adversaries.
Some of this is not open source. However, I can say that it may well have been into Japanese waters, at least briefly, as a test but more than likely they kept in international waters and are just playing cat and mouse games for the time being. They are coming increasingly close, though. It is still under investigation, i.e. as to exactly what they were doing over there on Sunday night.