He was unaware that he could claim, as he thought a) he did not have enough entitlement years, and b) he thought, even if he could claim, it would be "peanuts"...
Neither of these turned out to be the case. It was much better than he expected and better than a poke in the eye with a sharp stick...
(Not enough to live on it alone, but chips make a pile...)
The information in English on the Nenkin.go.jp website is mostly about taking a refund of up to 5 years of contributions if you leave Japan within the 10 year deadline for qualifying for the refund, and very little I could find about actually claiming your pension if you have more than 10 qualifying years...
I spent several hours at the Pension Office on the first visit confirming all the details, and about a month collecting all the required documents and completing all the forms before submitting them.
There are additional document requirements for foreigners living in Japan and overseas, but residents of many countries will be able to receive their Japanese Pension tax free, gross of withholding tax (there are some exceptions), subject to the terms of the tax treaty between Japan and the country of residence.
In this case, my friend had some years here as an overseas assignee, when he was not required to pay, and some qualifying years spent in the US, which helped get him over the entitlement line.
I will try to write up a reference doc in the near future, but if anyone has any questions, please ask them here, or contact the Local National Pension Office that handles your account. You will need your Basic Nenkin Number 基礎年金番号 - The Number in your Nenkin Handbook 年金手帳.