This review comes with no prior knowledge of the series as a manga.
Nana Maru San Batsu, Fastest Finger First, is a series about quizzes which, in itself, already makes it sound boring to start. Although it does do a decent job of making the subject slightly more interesting by emphasis of quizzes through Quiz Bowl competition, there still feel to be areas that are just lacking.
The premise is a bit bland but not something I have seen before, give a little praise where due. The story is a bit scattered for my liking with it feeling more like a slice of life that just happens to involve quizzing than a seinen title. The one strong suite is that the actual competitions are a actually quite interesting however, that could actually largely be attributed to character.
The art has no outstandingly low points but also few real high points. The characters themselves are fairly average. They aren't displeasing to look at and do have some nice emotion at times. The highest point for the art of the series though is the backgrounds. They're nothing groundbreaking or surreal but the backgrounds themselves are actually very consistent and well drawn. They often go unnoticed but that's not because they are bad by any means, they just feel natural and have good color balancing.
Annnnnd here comes one of the bigger issues in the show. The OP/ED for me are forgettable. Not a huge issue but good soundtracks always bring in a bit more of that special something to a series, even if the series sucked the music sticks. The biggest issue though is the character voice acting. As many have noted the voice of Fukami, Mari was definitely annoying at first and took getting used to but that alone can't warrant a score of 4. The issue is simply that the characters don't really feel all that alive at all. The VA is just good enough to portray some excitement and emotion when needed but it still feels forced. (This could partly be due to the slightly lackluster character illustrations as I noted before but I found it more of a sound issue altogether.)
The characters in the show are simply only moderately interesting. Aside from our MC Koshiyama, the others are interesting enough to keep things interesting but not delve further into them as individuals. The tropes that they fit into are actually perfectly average for what the show wants to accomplish and I see no fault in that. Koshiyama himself is the most interesting character, not as an individual but for his thought process during questions. Originally very straightforward and narrow minded in his approach he is quick to learn, adapting along the way and, thus, becoming more interesting. Him being the reason I mentioned that competitions are actually one of the strong suites of the series. Yet again though there are some glaring negatives. The show is about competitive quizzes but only a few characters really seem to realize or accept this. They also play around with what feels like obvious attempts at romance between Fukami and Koshiyama only to make things awkward, uninteresting and, altogether, annoying. Don't get me wrong I love me some romance but if it's not in your tags at all and is executed this poorly that just makes one cringe.
Despite the apparent flaws in the series there is still something in it I find endearing so I put it on the positive side of things. It is by no means a standout series for the season, although for this season that isn't saying much either way, but it does do a decent enough job of just being entertaining. There are some definite moments where you actually feel invested in the series and want to see more. You feel happy for the fun they have with their newfound friends and some nice little comedic bits do come in now and then. (As well as one of the most solid feeling second hand shame moments I have experienced in an anime thus far as well.) All in all it doesn't stand out above others but it can pass the time and be enjoying to simply watch.
The only thing that really truly bugs me about the series as a whole though: Is the feeling that it is just a poorly done Chihayafuru. It already had that feel for me from just the first few episodes and the way that her sheet was marked to count question measures by syllable. It only got worse when the anime itself kind of touched on competitive karuta. I do know that it is an entirely different activity but the way that it was all set up and the skillsets needed for both just made the comparison all too blatant for me and if you ever have to compare a series to Chihayafuru that is already a tough series to stand up to.
The series is relatively average as a whole with a few beacons of hope that are all but too short to warrant a higher score, thus far. I don't see a way nor find it likely that the show does a 180 and becomes super interesting from the progression of things but if the little things are done right more consistently it could be a solid 7-7.5 by the end of the season.