I 'found' (read rediscover after having forgotten they existed for so long) 2 streams where Mumei appeared but she was streaming at that time so it made me question if I had to add them in the collabs rentry because it goes against the rules I was committed to, that this rentry contains only collabs without a POV from Mumei.
1st one is Ina's POV during the 'I'm the (Sand)Man!' stream that spawned an imprompu 3-way collab with Sana (during the Cinnamon Roll Box incident).
https://youtu.be/e24Qsr3qLQA?t=119112nd is Sana's POV spawning another impromptu collab during Mumei's 'Home is where the HEART is!' stream of Animal Crossing: New Horizons (the 2nd stream from Sugar Rush).
https://youtu.be/ZfE66rwqc68?t=4416