The East China Sea is bounded on the East by the KyÅ `` shÅ `` and RyÅ `` kyÅ `` islands , on the South by Taiwan , and on the West by mainland China . 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 .