DRM stands for Digital Rights Management.
It is a technology that protects the copyright of digital data content.
If an adult video is subject to this DRM restriction, the following restrictions are listed below.
Net authentication (ID & Pass) is required on a regular basis.
Video files can only be played by players dedicated to video sites.
The video file cannot be viewed after a certain period of time after it has been downloaded.
The video becomes unavailable when copied to a PC other than the one from which it was downloaded.
When I cancel the membership of the site, the downloaded videos become unavailable.
Basically, most of the paid adult video sites in Japan seem to have DRM restrictions. In comparison, most of the paid adult video sites with overseas servers do not impose DRM restrictions on their videos and are DRM-free. As a user, I prefer DRM-free. It is advisable to check in advance whether the site you are considering joining has DRM restrictions on its videos.