I emphasise that this could be legitimate. However you are right to be cautious, very cautious.
I have seen fraudulent bank statements and utility bills that were not detectable from the real ones. When I was talking with the policemen involved, and asking how we would possibly know that they were fraudulent, he said that if you read the barcode and the account number, they didn’t tally. I quite rightly made the point as to how were we expected to know that.
I have known solicitors letter heads change hands and the solicitors firms and the names on the letters were legitimate. However, the scammers had reprinted the letterheads and change the bank details to their own bank details. The bank account actually existed although by the time it came out, the money had gone and the account was empty.
The more money that is involved, the better the paperwork!
Where is Wainwright-based?
With regard to the other two people who have allegedly sold through this organisation, do you have addresses and landline telephone numbers or just mobile numbers? Where are they based?
They are obviously asking for a chunk of money to release this. I can’t understand why that money cannot be deducted from the proceeds. What has the answer been to that?
What you might want to do is contact an organisation like this
to get them to put you in touch with a lawyer who would be able to translate all the documentation and do the necessary enquiries from contacts in Japan.