MAJOR SPOILER MAGIRECO

Mini Kyubey:

So, there's 3 girls, who for other spoiler reasons, dissect a Kyubey with their wishes. This results in the rings falling off the QB, and the smol QB that is there.
Unfortunately, one of them has a minor issue of almost becoming a full-on Witch. Or rather, their wishes were the foundation for Doppels, and this third girl was stuck in doppel and about to fully witch.

To stave off this issue, they temporarily store this third girl's consciousness inside the dead Kyubey they've got.

This third girl is Ui Tamaki.