So happy to see the consensus by all other reviewers, here, that this is already proving a *classic* anime series. It's been awhile since I loved a show this much (to the extent that I'm actually a bit fearful before each episode that it's going to suddenly slip into something less awesome).
The art/animation, voice actors, characters, character development, story/script adaptations, setting, soundtrack ... all of it is top-notch.
Zero is adorable. Her character seems a bit reminiscent, to me, of Seimei, the alchemist in Garo: Crimson Moon (powerful, independent, strong, intelligent, bookish, open-minded, and obsessed with food) and Toph from Avatar, the Last Airbender (hilarious, closest to Mother Nature, cynical but also vulnerable, a bit of a tomboy, etc.) ... plus her own precious self. As she appears so young, I appreciate that the artists/animators are not dwelling overly much on her 'sex appeal;' and I love that we continue to learn more about her past as she begins to feel a strong affection for the Mercenary.
The Mercenary is even more adorable than Zero, imo (and the voice actor, Tsuyoshi Koyama, is just excellent)! His character seems reminiscent, to me, of Shrek as well as the Beast (from Disney's B&tB) with maybe a bit of Gantu from the Lilo and Stitch series thrown in ... yet he, too, is also his own perfectly unique and deeply honorable self. I think what I fear most each week-- with respect to potentially falling out of love with this show-- is that he'll cease to be a Beastfallen and just become another boring ol' human. (And I mean, who even cares about the story of the Beast after he becomes a prince again, right?)
Too 'spoliery,' I think, to reflect here on Albus and Thirteen except to acknowledge that their melding story is becoming very intriguing! With only 4 episodes remaining of the 12 that complete the series (::sigh:: so few!), I can't wait to see what happens next.
Here's hoping we can all remain in love with this wonderful anime show!