They're mesmerizer and tiktok tourists, at least the proseka kids know about other songs outside the fotm from the last two years.
Sekai is also a bit overhated here, it's not nearly as good as project diva and the gacha scoring system is retarded, but it's an okayish free rhythm game with a generally good tracklist, except for some awful covers (and most of the vbs songs, but it's more of a personal preference). Also, grey miku and clown miku are cute