>>20837808sure thing, open wide:
tl;dr - you need to have a written permission to stream and monetize a video game in Japan.
Long version:
In Japan there's no such thing as "fair use." If you stream something and monetize the stream (superchats), a gaming company can copyright strike your channel at any time. Hololive and Nijisanji are Japanese companies, so the Japanese laws apply to them.
That's why the companies need to have written permissions to stream games. You might think it's a stretch, but there were multiple cases that companies struck youtube channels of vtubers, causing them to lose all monetization and have hundreds and thousands of videos private/deleted. Sometimes the permissions are time-bound, for example all of hololive played pokemon for a specific period of time, I think one month, before the permissions expired.
Theoretically, those companies can do the same thing for western vtubers/streamers too and sometimes they do so, however an indie losing their GTA playthrough rarely makes a noise loud enough to be noticed.
Cover and Niji have learned their lessons and know they need proper permissions. Some permissions are available only to one company or even one vtuber, for example Metal Gear Solid is only available to Nijisanji.
There's currently no reliable information what sort of talks happen between game producers and vtuber companies, but I assume it sometimes involves bribing/sponsored content/etc. It's a tough business world.
