What's this from? I've never heard of "Virtual Youtuber" before, is it just fanarts of random youtubers or is it an actual series? Kinda confused lol.
They're youtubers who streams games and stuff in the form of anime characters. I think Kizuna Ai is one of the famous examples. She's pretty popular. But Okayu and Korone are from a company called Hololive.