Quick definitions from WordNet (Inland sea)
▸ noun: an arm of the Pacific Ocean in southern Japan; surrounded by the islands of Honshu and Shikoku and Kyushu and linked to the Sea of Japan by a narrow channel; the chief port is Hiroshima
▸ noun: an arm of the Pacific Ocean in southern Japan; surrounded by the islands of Honshu and Shikoku and Kyushu and linked to the Sea of Japan by a narrow channel; the chief port is Hiroshima