I know nothing about Rage of Bahamut except for the fact that the series exists. But given how highly I've rated Manaria Friends, you'll probably expect that you don't need to know anything about Rage of Bahamut to enjoy this gem of an anime, which indeed proves to be the case.
Manaria Friends is, on the surface, little more than a carefree story about two good friends. It doesn't try to overcomplicate relationships, or introduce malevolent external elements in order to artificially temper the centerpiece friendship between Anne and Grea. It's as straightforward a show as you can get, with no bumps in the road throughout all ten episodes. But therein lies the beauty of an anime such as this.
Premise (2/5): I was surprised to learn that this anime was linked to the Rage of Bahamut series in any way, and even after finishing the anime, my surprise has yet to subside. There's really not much to learn about the universe of Manaria Friends as a whole, at least not within the confines of the anime.
The blurb on the anime site I used to watch this show spoke of a conflict between the nations of Anne and Grea, who are both princesses of their respective countries, but there was never an opportunity to learn about the finer details of those nations, nor anything in the anime itself to suggest that a war had ever taken place. In some ways, Manaria Academy's isolated location is a reflection of Manaria Friends' separation from the Rage of Bahamut series as a whole, which works just fine for me since I have little desire to chase after the main series. Maybe some of the backstory's potential is squandered somewhat, but considering how laidback and simplistic the anime is, this isn't anywhere near a major complaint.
Manaria Friends is set largely within Manaria Academy, with the occasional scene in the town outside the school or in the palace inhabited by the royal family to which Anne belongs. That's all you need to know, because that's really all they give you.
Characters (5/5): It's tempting to write Anne and Grea off as monochromatic, one-dimensional, tropey characters, but that would be paying a great disservice to the symbiosis between their individual personalities and their interpersonal relationship. The plot is essentially a chain of seemingly small incidents that serve to simultaneously reinforce Anne and Grea's bond and remind each of them of the importance of their friendship, tracing a line all the way back to the day their eyes first met in the abandoned school building, where Grea had been playing the piano on her own.
The stages of character development for both girls are subtle and gradual, yet they give rise to one of the most beautiful and heartwarming friendships I've seen in any anime, particularly because their friendship always teeters on the edge of romance, but never quite falls far enough. Anne's secret loneliness and desire for true personal amity naturally finds its tonic in Grea; Grea's reticence and introversion is eased in turn by the confidence and competence of Anne. Nowhere is the strength of this friendship more evident than in the penultimate episode, where all it takes for the two of them to make up after a fight is for them to sit alongside one another and enjoy each other's company once again.
The minor characters are equally multi-faceted in their own ways, and all of them play their parts well - Hanna, for example, is the ostensibly upstanding student council president whose stumbling attempts to compensate for her supposedly inferior talents (at least compared to Anne) provide a source of humor and good cheer. Thankfully, none of the minor characters ever feel overly intrusive, and the main characters are allowed to get on with what they need to do.
Audiovisuals (5/5): What more is there to be said? Screenshots of the anime will probably tell you enough about how well done the background art is. The ocean water laps against the sand and glitters in the midday sun, each wave painstakingly drawn and animated. The abandoned school building's dereliction is covered in meticulous detail, but the green vines snaking around its stone walls lend it a vibrancy that few other old stone structures in anime seem to embody. That's not to say the character art is lacking in any sense - it's as good as you'd expect it to be, with a sprinkling of fanservice here and there. Certain additional details, such as the serpentine twitching and twisting of Grea's tail depending on the emotions that she feels, help provide different means of conveying each character's internal thoughts. Combine all of these facets, and you have a visual spectacle rivalling that of any anime out there.
The soundtrack is admittedly a little hit-and-miss in the first few episodes, especially when the theme of the music is out of sync with what's actually going on (e.g. having overly dramatic music in a relatively calm scene or vice versa), but those errors of audial judgment are ironed out by the end, culminating in a spectacular insert song in episode 8 and a piano-driven repertoire that elevates the serene atmosphere of the anime to an indescribably comforting and satisfying level. The lack of an opening segment is just fine with me, since I usually tend to skip those, and the ending credits are short and sweet, featuring miniature picture-frame snapshots of the episode's events. All in all, this is perhaps the standout aspect of Manaria Friends.
Execution (5/5): Of all the genres that this anime might be considered, slice-of-life may not be everyone's first thought. Yet the slow-and-steady pacing and episodic nature of the storytelling are reminiscent of most typical slice-of-life anime, even though the "ordinary life" experienced by the students of Manaria Academy is significantly different from the version that we may be used to. Manaria Friends takes its fantastical elements for granted, and the confidence with which it assumes the normality of magic and other elements that may be unfamiliar to us is refreshing, to say the least. Those who aren't the biggest fans of slice-of-life anime (like me) may be wary of stepping into an anime like this, but at no point did I ever feel turned off or bored by watching the two main characters fumble their way through a sparkling and blossoming relationship, and for that I'm immensely grateful.
Manaria Friends dabbles in many different things, but always makes sure it keeps its final objective in mind. The humor is tasteful, but never overriding. The pseudo-romance is burgeoning, but never blatant. The drama is tangible, but never forced. It's a simple story set in a complex world, yet Manaria Friends is content to let that complexity go if it doesn't advance the progression of the friendship between Anne and Grea. The result is a show that is far more than the sum of its already impressive parts.