I was in the Navy at Yokosuka and I totally understand. No is the easiest answer. It's probably best to go directly to the source that will be checking your shipments and allowing them or not. But be careful what you wish for. Okinawa is not that big and if you draw attention to yourself, they may just be on the lookout for your name when juice comes in.
Can't find it now, but a while ago someone posted about an online shop that sold nic juice. When I read the site, they were basically drop shippers. They would order from the vendor and have it shipped to the person. Maybe that would be another avenue. Maybe you become a go-between. Order yours on a personal basis, have people try them in your shop and be the middle man by making the orders online and having them shipped directly to your customers. Japanese customers would like that, many of my Japanese friends don't know what to get and can not speak enough English to understand the ordering process. But they like it when they try it.
So, I do that for friends and family that I have switched to e-cigs. I stay under the "1month"/"120ml" by doing that. I just add in the shipping costs and could probably add in some type of handling or processing fee. They pay me up front.
Here's one box, got a lot of samples here. But they are not for sale. This is my personal vapes.
