Map of QSLed Japanese Prefectures.

Mapchart.net is a nice tool to create maps for free.   

Here is a map of all the Japanese prefectures I have QSLed so far.

https://www.mapchart.net/japan.html

Seeking information about Japanese QSLs?

Thanks to Koji Shimotori I found out that "ベリカードについて" (vericard) is an interesting Google search term when seeking information about Japanese QSLs.

QSL card "ベリカード"

QSL letter "ベリレター" 

QSL "受信確認証"

Reception Report is called "受信報告書"

Don't forget to use also other search machines like Bing or DuckDuckGo. They give often different results.

I never thought that some stations should provide info about QSLs on their website. Here are a few examples.  

JOYR RSK Sanyo Hoso : https://www.rsk.co.jp/company/qsl.html

JOKF RNC Nishi-Nippon Hoso : https://www.rnc.co.jp/vericard/

JOBF RKK Kumamoto Hoso : https://rkk.jp/companyinfo/qsl/index.html

JOJF and JOPF YBS Yamanashi Hoso : https://www.ybs.jp/verification/

JOWR, JOWO, JOWE, JOWW, JOFL, RFC : https://www.rfc.jp/company/veri_card.html