The Ancient Magus' Bride, Volume 8

Chise may have stopped the dragon's rampage, but at a great cost: she has been cursed, and a dragon's curse is unbreakable! Chise and Elias are visited by Marielle the witch, whose fellow witches claim to know the secret to helping Chise. There's one catch—in exchange for their aid, Chise must join the witches' coven.