I simply sent them an email, and they responded fairly promptly and were helpful to supply the product, and I then found a local compounder to put it in dosed slow release capsules, which is very important because of the small dose and the fact 4-AP is basically bird poison. The other thing to note is, that it really needs to stored carefully to avoid degradation (ie oxygen, water, light etc).
Also, in Australia there is a govt agency which controls the importation of medicines. They have a specific process to import unapproved medicines such as Ampyra. You may find that Japan has a similar group, and therefore possibly a similar process to access Ampyra.