Okinaw

Okinawa hasn't always been a part of Japan. From the 15th Century when the island was unified under a single king until it was annexed by Imperial Japan in the 19th Century, Okinawa was an independent kingdom called the Ryukyu Kingdom. The Kingdom traded with both China and Japan and was significant enough for Japan to take unofficial control with an invasion by Samurai from Kagoshima in the 17th Century. Interesting enough, the king who unified Okinawa claimed he was decended from the Minamoto (Genji) Clan, a military off shoot of the Japanese Imperial Family.
After World War Two, America controlled Okinawa until 1972 when it reverted back to Japan. There is still a major American presence here with one of America's three marine divisions split between here and Guam.