Sea of Japan or East Sea, enclosed arm of the Pacific Ocean, c.405,000 sq mi (1,048,950 sq km), located between Japan and the Asian mainland, connecting with the East China Sea, the Pacific Ocean, and the Sea of Okhotsk through several straits. The shallower northern and southern portions of the sea are important fishing areas. The sea has depths of more than 10,000 ft (3,050 m). A branch of the warm Japan Current flows northeast through the sea, modifying the climate of the region; Vladivostok , the only ice-free port of eastern Russia, is here.