There's a sting of bitter irony in the fact that Re:Creators, an anime about anime, will probably end up being defined by its meta-narrative in the long run. The show itself was in possession of an interesting premise, a knack for visual flair (sometimes sadly disrupted by cheap CGI), and a tendency for better and worse to pile odd plot kinks on top of each other, leading up to a conclusion that has been alternately praised for its unusual direction, and denigrated for allowing the main villain to essentially get away with everything.
In spite of the mixed reception, though. Re:Creators had an admirable amount of ambition, characters who often managed to step outside the logical bounds of being direct xeroxes of well-worn cliches, and a really damn cool villain. Despite, or maybe because of, its ambition so vastly outstripping what it could reasonably do, there was a real charm to watching the series work itself into knots, and even just in watching the cast interact. So it's not particularly surprising that it did enough numbers to get a manga adaptation, and that that adaptation had a spinoff. What is surprising however, and what is probably most damning about Re:Creators One More, is that it possesses exactly zero of that charm.
Maybe it's a bit overly blunt to lead with that, but it's the honest truth. There's nothing wrong with One More per se, it's not horribly written, the art is good and nicely expressive (although its resemblance to the series' art is pretty thin), but there's a major problem in the fact that it takes place during the exact same time frame as the show, and as such, it writes around the series' plot and attempts, on that, to awkwardly graft the non-story of hardcore otaku Miharu. Miharu is not the most interesting protagonist. There have definitely been worse, but "otaku girl" is not anything super new, and a good chunk of her characterization is her devotion to her fictional "husband", Sho (who did indeed appear in the later episodes of the main series), and her quest to meet and marry him. She has a daki, that sort of thing. Occasionally, she will humorously misinterpret an event from the main series. For instance, attributing the sudden appearance of a new design for Selestia as the author's "burning passion" overflowing and causing her to manifest in the real world. She also has the slightest bit of extra depth in that she's an amateur mangaka herself, and is apparently rather insecure about her work (whether this is a subtle bit of self-insertion by mangaka Yuuki Kumagai is left as an exercise to the reader). Miharu is far from unlikable--in fact in terms of immediate likeability she's probably doing better than main series protagonist and famously vanilla individual Souta, but she's just not that interesting.
######Protagonist Miharu is certainly cute, but, well, not much else.
---Part of the original Re:Creators' strength is that the Creations (inexplicably the term "manifested character" is used here instead) felt like anime characters, and the Creators felt more like real people. Comparatively down to earth and subtle. Miharu seems more like an escapee from one of any number of slice of life comedies than an actual person herself, and the same is true of her two classmates that comprise the rest of the "real person" cast, and this really is the manga's main writing flaw. Miharu treats everything like a game (partly due to not having the context of the main series that we on the other side of the fourth wall do) and part of her quest to meet Sho. There's no real stakes here, just a girl and two of her friends kind of shuffling around behind the scenes of Re:Creators and saying and doing goofy things.
######Yes, the manga does feature both of these old-as-sand gags in its meager six chapters.
---Funnily enough, the character that actually steals the show is main series transplant Mirokuji, who essentially tells Miharu off for treating their suddenly very real struggle as a means to meet her huzbando. When she finally does meet Sho in the manga's penultimate chapter, he's weirded out, and after gushing to him for some indeterminate amount of time, Miharu has her phone shot to pieces by Blitz Talker in what is undeniably among the funniest scenes in the manga.
The manga's final chapter is devoted to Miharu (now in an understandable funk from being blown off by her favorite fictional character) and her friend attending the Elimination Festival. What this means in practice is that we're treated to a cliff's notes of the actual events from the main series, intercut with visually well-done but plotwise meaningless shots of Miharu enjoying herself. Afterward, a still-bummed Miharu is cheered up further by reconciling with Shou and Mirokuji. She laments (before being cheered up. Again) that she's "merely an observer" and "not the main character, not the heroine". The tragic irony here is that she's actually right. In spite of what's presumably supposed to be an empowering finale, Miharu really isn't the main character. Because this isn't her story, it's Re:Creators' story, which she has been awkwardly written into the sidelines of.
Given her own series, and more than six chapters to develop as a character, Miharu could probably actually be a decently interesting protagonist (the series' funniest joke is its very last, where she draws a doujinshi of herself and Sho, it is absolutely the sort of thing that an obsessive fangirl sort would do, and it's much more original than the billionth "look at all her merchandise!" joke). But here, scribbled in the margins of a story that's not her own, she doesn't have that room, and there's something again kind of bitterly ironic about that. Even the most cliché of characters deserve better.
######In addition to the occasional more clever gag, it's really Kumagai's command of art, especially facial expressions, that are redeeming factors here
---If there's a silver lining to be extracted, it's that Kumagai can certainly draw, and this is probably not her last rodeo in the medium (she had an ongoing serial even before starting work on this series). It's hard to believe that there are not brighter horizons ahead for the talented young artist, and maybe in those stories--that have yet to be written--a sort of retroactive place for the character of Miharu can be found, as a symbol of potential yet-unrealized. And really, what is Re:Creators about if not taking control of the narrative?