Many times, I pretend that I've taken the picture and then wait until the face relaxes from a seemingly forced smile and the hands drop. Take more than one photo when permission is given. After the first click, most people assume you are done and on many occasions it is the second or third shot that is the prize. In my experience of photographing close-ups I have found that many more men are willing to agree to the adventure than women. I have gotten older women to agree to the experience.
Young women love to be photographed and enjoy the attention.
I have also found that although I don't use the money tactic often, a single five-hundred yen piece has brought on a sudden agreement of consent to be photographed on many occasions. In many of the third world countries that I have visited, you will be expected to pay your subjects a small price to be photo'd. It is the norm in countries such as Egypt, South America, Haiti and Russia. In other countries such as San Lucas and parts of the Caribbean, posing and money is generally refused. I have not found this to be the expectation in Okinawa, nor in Mainland Japan and if handled poorly, might be considered an insult.