In China , the sea is called the East Sea . The East China Sea is bounded on the east by the KyÅ `` shÅ `` and Ryukyu Islands of Japan , on the south by the island of Taiwan , and on the west by mainland China and the Asian continent . It is connected with the South China Sea by the Taiwan Strait and with the Sea of Japan by the Korea Strait ; it opens in the north to the Yellow Sea .