From the map, I can understand the island is belong to China or Taiwan (they are pretty close), I still don't understand why Japanese still consider it is part of their land.....
If you have time, try play around with google map. In the Pacific region (Soloman, Marshall, Guam, Fiji, Tonga...), you can realize it is such a "mess" for the islands around. US, UK, France, Japan... islands everywhere... If there are people living, you can still say so it's being occupied. But for those no man land, it's just based on how much muscle you have...
If you don't patrol the area with your fleet, it's totally useless. US and Japs won't give a flick how loud you bark and how much evidence you have in proclaiming the ownership.
Actually, Okinawa islands should also be part of China, but was taken away by the Japanese.
The Chinese need to take back territories one by one as they become stronger.