This picture confirms 2 things.

1) Yui is indeed the human who became Charlotte.
2) Yui is still retarded as she wished for an unlimited supply for cake, as we can see in Charlotte's witch zone.

@Ola
Spoilers, bro.

Kyubei needs to leave K-on alone!

NO
Make your contract with Gitah!

akumaten said:
NO
Make your contract with Gitah!

That's actually Charlotte's wish.

I wish this artist could draw legs.

ive been noticing that yui is becoming a cosplaying char here