Gura got replaced by Mumei.

Gura ghosted management sometime after Holloween, so management started a plan to replace her. Mumei would take the roles of both herself and Gura. The first stream Mumei took over was in December after Gura had been gone for 3 weeks. https://www.youtube.com/watch?v=L3tOeOV2VOo It starts with "Gura" speaking gibberish and ranting about "football" in exactly the same manner as Mumei would. Haven't you ever noticed that they haven't collabed or interacted on stream at all since October? That's because they can't because they are the same person.

Mumei is Gura now.