Snowden warned June 3 2016 that people in Japan are subject to mass NSA surveillance and that the US is responsible for pushing for the Act on the Protection of Specially Designated Secrets, or Japan's recent and much reviled state secrets law:
Shusuke Mura. NSA whistleblower Snowden says U.S. government carrying out mass surveillance in Japan. Jun 4, 2016 http://www.japantimes.co.jp/news/2016/06/04/national/nsa-whistleblower-snowden-says-u-s-government-carrying-out-mass-surveillance-in-japan/#.V1RhAeSYJmw
Officially known as the Act on the Protection of Specially Designated Secrets, which went into effect in 2014, the law gives ministries and agencies discretion to classify information in areas such as defense, counterterrorism and diplomacy as state secrets. Leakers, including civil servants, could face up to 10 years in prison and those who instigate such leaks, including journalists, could be subjected to five-year prison terms.
The law was steamrolled through the Diet in 2013 by the administration of Prime Minister Shinzo Abe despite a mass public outcry over the obscure nature by which information will be designated as a state secret.
In an interview with the weekly magazine Sunday Mainichi in its Tuesday edition, Snowden said the enactment of the controversial law was requested and designed by the U.S. government to facilitate the NSA’s espionage activities in Japan.
I've published quite a few posts on Japan's state secrets law. Here is background information:
Japan's Troubling State Secrets Law Takes Effect | The Diplomat