Although Steam has a handful of Hololive vtuber games already—that is, games featuring members of the popular vtuber agency—none of them are as comprehensive as Hololive Dreams. A rhythm game with a huge list of collectible characters to meet, Hololive Dreams is the closest thing we're getting to a vtuber theme park—at least until someone builds one in real life.
It's also a pretty good starting point for anyone who has only tangentially heard about Hololive, one of the biggest vtuber agencies around. The game offers more than 150 songs to play, some of which are covers of tracks from artists like Babymetal. All the biggest hits are in there, with more coming in the future.