Mamiya Rinzo, an Explorer Who Discovered that the Sakhalin is an Island He was an explorer of the Yedo period who found a strait between Sakhalin and the Eurasian continent. This was later named the Mamiya Straits in his honor. He travelled the northern region all alone and reported his findings to the Yedo government. This spectacular feat was achieved in 1809. His monument stands on the shores of Cape Soya where he started his lonesome journey and is facing the Sakhalins.