Minami Kojima Island Upd Now

It seems you're referring to (南小島), which is one of two small islets (the other being Kita Kojima ) that make up the Senkaku Islands (known as Diaoyu Islands in Chinese). These are located in the East China Sea. The sovereignty of these islands is disputed between Japan, China, and Taiwan. Japan administers them as part of Ishigaki City, Okinawa Prefecture. If you need more details (geography, history, or the dispute), feel free to ask.