Linked from
The 7 pages that link to Kanmon Straits, each with the reason it gives.
KyushuRelated: This passage links Kyushu’s transport networks with Japan’s largest island.
Yamaguchi PrefectureRelated: The strait makes Shimonoseki a major transport and shipping gateway.
Bungo ChannelRelated: It is a western entrance to the inland sea on the opposite side of Kyushu.
KitakyushuRelated: Its location makes Kitakyushu a gateway between Kyushu and Honshu.