Korone as in her appearance on gameheaven or am I missing something? If that's the case then Okayu, Mio, Coco, kson, Botan, and I'm sure a few others count. But, if that's what you're referring to I don't really agree. They just made appearances on there while being their own individual person. Similarly to how Fubuki, Aqua, Shion, Pekora, Watame, etc were just some Niconico streamers/content creators.
Fubuki has mentioned in the passed how she was friends with Mio, and how Mio in turn got Fubuki in touch with Korone and Okayu. If I remember things correctly anyways.