There were originally virtual YouTubers who liked online sandbox games.

It wasn't particularly strange for those virtual YouTubers to gather and open an Underworld server.
Of course, it would be even better if they could make money through Underworld broadcasts.

First of all, for Underworld broadcast content to become popular, the more virtual YouTubers participating, the better.

The appeal of Underworld is that it's a troupe drama based on RP (role-playing), and that another self living in another world meets various connections.
So it's fun if there are always a lot of residents, and the more virtual YouTubers participate, the more viewers will always watch this broadcast.

However, what good would it do to gather 200 virtual YouTubers who only have about 10 viewers?
Sora alone can easily mobilize that number of viewers.

So it's not enough to just have a lot of virtual YouTubers participating, popular virtual YouTubers also have to participate in Underworld.

At that time, the Fantasy League was gaining popularity in the virtual YouTuber industry.
Since the virtual YouTubers participating in the Fantasy League were also gaining popularity, it was only natural that the Underworld management would try to seduce them.