Okinawa is 2 hours or thereabouts and Amami Island is 1 hour from Kagoshima, all with daily flights.
Tokara is very possible and very good season during July. You would need to fly to Amami in order to fish Tokara with Captain Fukui. There is another boat in which you catch a long-haul ferry from Kagoshima Prefecture (12 hours or thereabouts) to one of the Tokara islands. I certainly prefer Captain Fukui, irrespective of not fishing with anyone else before, because I can fly to Amami and then get on the Big Dipper which takes roughly 2 hours to arrive to the Tokara Islands from Amami.
You will need to enquire NOW because it is not unsual for the Big Dipper to be booked out 6 - 12 months in advance during all slots. Even then, you will need to join a group.
I will be fishing Tokara for 2 weeks in July, so I will enquire directly with Fukui-San if there is additional vacancy for you.
Trips are 2.5 - 3 days each in which the Big Dipper must return to Amami island for more fuel. Tokara is very remote with minimal facilities. The fishing I would describe as difficult and not for beginners - but there are BIG fish there that will be caught with perserverance. Seas can be rough but the Big Dipper is a very seaworthy vessel perfect for GT popping and Captain Fukui's skills and courtesy could be described nothing less than exemplary.
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Most charters are based in the south of the island and acustom to individual bookings to make up a group of anglers.
Maeda-San visits southern Okinawa and out to Kerama - The Kerama Islands is where Kozo Okubo recently caught a 70kg GT on popper, and claimed as an IGFA record. There seems to be a healthy populations of 20 - 40kg GTs, with the possiblity of much bigger also available. The Keramas are approx 1 - 2 hours by boat from Naha.
The northern part of Okinawa is home to a charter operator who is also field tester for Shell-Shaping Lures. He was extremely professional and the scenery is superb in the north along the big cape.
I will ask David Clumpner for more information and contact details as I have difficulty translating their websites.
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You can also fish from Tanegashima, which is way more accessible than the other options listed.
There are big GTs caught there every year but they are few and far between due to pressure.
I will have a contact for you soon...
Luke