в закрытых конвертах что-то берется только из полиции, как правило при подаче на визы в страны типа США

Ну, написано на сайте у них:

Those who would like a copy of their "Pension Coverage Regular Notice" (Nenkin Teiki Bin) (a document which list all of the recipient's pension records to date) may submit an application with the Japan Pension Service, using the contact information listed below. When submitting an application, please state that "全期間分(封書)を交付希望" - that you would like "documents for the entire period, in a sealed envelope." (It will take around two months to receive the documents.)

читай не только этот пункт, но и дальше:

Applicants who have been continuously paying into the national pension plan for the past two years (24 months) and are able to submit a copy of their pension payment receipts do not need to submit the items listed in a and b above.

А откуда брать эти чеки, кстати? Это та открытка что приходит иногда?

into the national pension plan

какие чеки. из ненкина справку распечатай и все

о, я тоже жопой читаю

правильный ответ вот:

Those who are paying into pension plans other than the national pension plan (such as employee pension plans) should submit the documents listed in either a or b.