A couple nights ago Amiibo wave 4 came up on amazon.jp and I scrambled to figure out how to use a forwarding service (Tenso.com) to get them. Some things can be ordered directly from Japan to the US, but some things cannot. Unfortunately, Amiibo figures can not be directly purchased from amazon.jp.
Overall, it wasn't that difficult to get everything set up, but once I did and confirmed everything was right I felt a lot better about the process. Below is my best attempt at a step by step guide (with pictures) to help anyone that is new to the process.
I live in the US and was pre-ordering Amiibo figures from amazon.jp so this guide will be from that point of view.
Register for an account on Tenso
Your first task is go to the english version of Tenso. There you will see the screen below. Click to register a new account.
Signing up is fairly straight forward. Enter your personal information and billing information.
After signing up you will receive an email with some important information. Seen in the image below is all of the address information you will need to give to amazon.jp. Most of the address will be the same for everyone signing up (postal code, region, street address, phone), but what is different is your unique Tenso ID. This takes the form of TSXXXXXX. The ID also shows up in address line two as TSXXXXXX転送コム. The japanese part means "transfer com".
Also important within the email is the link to prove your identification. My understanding is Japanese law requires proof of address before shipping goods overseas. It is pretty simple, just scan an ID and upload a photo. This only needs to be done and verified before your item ships from Tenso's warehouse (more about that later).
Purchasing from Amazon.jp
The best way to navigate amazon.jp is using Google Chrome since it has a translation feature. Once the page is translated, use the drop down menu to sign up for amazon.jp. Unlike amazon.co.uk/fr/de/etc, our US accounts are not linked with the Japanese amazon so you'll have to create a new account.
Sign up is fairly straight forward with google translate so just fill in all the required fields and create a password.
Once your account is created, while logged in use the drop down menu and select "Account Services". See the image below to find "I want to change the contents of my address book".
This next step is probably the most difficult part of the whole process (still really easy). Click the button "to enter the domestic address" and you will be taken to the screen you see below. You will need to enter in the information from your email. Revert the page back to Japanese and enter:
1. your name in the first space
2. the postal code (120-0023) in the second space
3. The region in the drop down menu (says "Tokyo") make sure to match the characters from the email
4. The address from your email up to "42-4". In the email the lump the two address lines into one line, be sure to split them up.
5. The second address from your email. This is the TSXXXXXX転送コム part.
6. Leave blank
7. The phone number (03-5739-3341)
All these steps are also illustrated here.
Okay, rest assured that if you followed these steps correctly amazon will not send your package off to Okinawa. Now, after you finish with your address billing information will come up. Use google translate again to translate the page. Click on the "Enter the information for the new payment method:" radio button and it will bring up the image shown below. You can enter in your credit card info here.
Okay, now you are all done. Just buy Amiibos like you would on the US page. Add them to cart, then proceed to checkout and ship to the address we entered in earlier. Once Tenso receives your items they will update your shopping page on Tenso.com within a day (or so). Then, assuming that your address was verified, they will ship the items to you. All that's left is the security of pre-ordering wave 4,
Q: How much does each amiibo cost?
A: Well, this is a complicated question so the short answer is, it depends. It depends on the exchange rate along with the number of Amiibo and the shipping weight. The best resources I found are listed below:
1. Exchange rate calculator. Each Amiibo sold by amazon is ¥1,296 or $10.91 when this was written.
2. Tenso Fee Guide/Tenso Shipping Fee Estimator. Tenso charges based on the weight so if I order all of wave 4 that is 6 Amiibo figures. Assuming each figure weighs ~90g, the weight of the figures+box would be around 650g. Using the cheapest shipping method this is ¥1,750 or $14.74. So, if you pre-order all of wave 4 your approximate total charge would be $10.91*6+$14.74=$80.20 ($13.37 per amiibo). That is cheaper than MSRP+tax and only $2 more than MSRP when buying all 6. That's actually pretty good. Of course it all depends on how many you order and what the actual weight of the package is.
Q: What is the shipping speed?
A: You can choose various shipping speeds and information is provided in the Shipping Fee Estimator. The cheapest option is approximately 14 days.
Q: Is it reliable?
A: Unfortunately, this is my first time using Tenso so I can't speak from personal experience, but if you search Tenso on /r/amiibo it appears that it is a trusted service.
Approximate Cost per Amiibo
Assuming the amazon price of ¥1,296 (even though they do get cheaper) and an approximate weight for each Amiibo at 90g, and a box+packing material weight at 350g (I weighed a pretty large box with some bubble wrap and rounded up), below are some estimates for cost per Amiibo. I've decided to over estimate everything to be safe so these should be fairly high values.