Zettai Bouei Leviathan tells the story of a trio of dragon-girls on a planet named Aquafall that is occupied by dragon-people. At least, some of them are dragon-people, as we see non-dragon denizens milling about over the course of the show. One day, Aquafall starts getting pelted with meteorites that contain insects known as Lucasites who start invading the planet for an unspecified reason. In order to put up some resistance, the fairy Syrop goes on a journey to establish a team to defend Aquafall from these insect invaders, but, instead, she just ends up relaxing for a while with the first three girls she comes across and calls it a day. Once she infroms the girls that their planet is in grave danger, they all rebuke her, so she decides to stick around and convince them to join her team. That's right. The world is in grave danger and in her quest to form a team to save it, she asks the first three people she finds to assist her. Strangely enough. nstead of going and finding teammates who are actually interested in saving the world or who even have the skills required to do so, she decides that these three are her only options and spends an inordinate amount of time pestering them.
Granted, the story is mostly non-existent, but to be fair, If you decide to watch this, you're probably not here for the story. For the majority of the show's run-time, the characters just sort of hang around and do nothing, with the occasional cgi bug battle thrown in. However, for the most part they just go to the beach, eat, or visit a hot springs. Additionally, this anime acts as a prequel to the game, so the plot doesn't even really kick in during the show. In other words, if you want a story, I'd suggest looking elsewhere.
As far as the characters go, they unfortunately don't fare much better. The cast mostly consists of the four main characters; Leviathan, a timid water-user, Bahamut, a selfish fire-user, Jormungandr, an adventure-loving warrior girl with an ax, and Syrop, a useless fairy that isn't good for anything other than food jokes. There's very little depth to the characters, who are best described as vague, color-coded archetypes. Although there is a bit of character development here and there, there isn't enough of it to make the audience care about any of them.
That isn't to say that the characters are particularly unlikeable, but their mannerisms and interactions can certainly be quite grating at times. Leviathan is obsessed with finding her brother, Bahamut has daddy-issues, and Jormungandr comes from a loving two-father family (which is something I've never seen in an anime before.) Syrop on the other hand is just annoying. We never learn anything about her and her comic relief moments are all so interchangeable that it's a wonder they exist at all. Bahamut is also extremely whiny and selfish, so she tends to grate on the nerves as well. On the other hand, Leviathan and Jormungandr are mostly non-offensive, so at least the major cast members aren't all annoyances.
Interestingly enough, Zettai Bouei Leviathan comes courtesy of Gonzo; the once powerful studio that famously imploded, only to slowly start building itself back up without any of its real talent on board. The lack of vision in the staff is visible throughout many aspects of the production. That is to say, Zettai Bouei Leviathan is extremely bland and generic to look at. The character designs are bland and extremely basic and the background art is the same type of typical fantasy fare that you can find anywhere else. There was absolutely no creativity expended on the characters, nor the world that they inhabit. That's not to say that they're badly drawn or anything, but everything is simply as cookie cutter as can be. Significant portions of the show take place in such interesting settings as Generic Fantasy Town and Generic Desert. All in all, the art isn't interesting to look at, which extends to action sequences and enemies. All of the Lucasites and dragons are rendered in CGI and while they don't look terrible, their appearance shares the same weaknesses as the rest of the art. They're completely non-threatening looking and, once again, extremely generic. The animation is much the same; it gets the job done while doing the bare minimum.
The girls also have transformation sequences, but these are boring as well. Each one just shows the characters wearing scale underwear (because they're dragons, or something) at which point they put on magic outfits and grow wings on their sides and heads. The fights are also very uninteresting to look at. When it comes to attack variety, the characters leave much to desire. Leviathan conjures water-tentacles to grab her foes, or throws water projectiles while Bahamut either throws fireballs or uses a stream of flame, while all Jormungandr does is hit stuff with one heavy swing of her ax. The battle scenes are few and far between, so they're not THAT redundant, but they do come across as rather lazy.
Then we have the voices. Despite how mediocre every other aspect of the show is, Zettai Bouei Leviathan has a fantastic voice cast made up of Saori Hayama (Ayase in OreImo), Eri Kitamura (Saya in Blood+), Ayana Taketatsu (Kirino in OreImo), and Kana Hanazawa (everything ever.) These talented actresses all do the best they can with the material, which, although it isn't much, helps to muster at least some enthusiasm for the series. They do sound a little bored, though, especially Saori, which is hard to fault her for, considering the monotone nature of her character. Still, the voice acting is the sole bright spot in the series. Why they got a star-studded voice cast and left them to languish with such mediocre material is beyond me, but if there's any reason to watch the show, it's them. On the other hand, the music is completely forgettable and not even worth mentioning.
All things considered, Zettai Bouei Leviathan isn't terrible. There's nothing particularly offensive about the show, but it is extremely boring most of the time. It mostly plays like an extremely long advertisement for the game and it feels like it only exists to spread the word and fill air time. Overall, I wouldn't recommend this show to anyone, but I wouldn't moan and groan about it either. There isn't much to like, but at the same time, there's not much to hate either. If you just want a bland, fantasy show with a great voice cast and cute characters, you could certainly do worse than Zettai Bouei Leviathan, but there are much better shows to spend your time on.
