Fans panicked, went nuts, and generally shat brix. Then she showed up in the Magical World out of nowhere as a demon lord on the side of the bad guys. Akamatsu claimed he'd reveal the secrets around her in the final arc. For most of the series, the character of Zazie was a total mystery, with no development or Backstory whatsoever, although something was clearly up with her. Not to mention the whole 'Zazie's identity' thing he pulled.* Well, he did deliver on the promise, he just didn't say that it was. Followed by messages on Twitter saying a sequel is probably coming.
Just look at how he ended the manga after years of Ship Tease galore. Ken Akamatsu of Negima! Magister Negi Magi.
In retrospect, this may also double as Torch the Franchise and Run for the author. Fans eagerly waited four months only to find that this epilogue was nothing more than a few panels of the boys dreaming about the Wet T-Shirts Contest with neither background explanation nor conclusion. The final serialized chapter was released on December 2017 with an abrupt Downer Ending, with the author promising a 'much improved' epilogue on the release of the final volume (April 2018).
