Few things disappoint like an intriguing idea degenerating into a missed opportunity. Few things exhilarate like an intriguing idea that's just the starting point for one great leap after another. Birdy The Mighty: Decode, vastly expanded from an earlier OVA adaptation of a manga, begins with a premise that would be fun even if it were used for nothing more than a goofy comedy. Then it spirals out wider and wider until the original premise all but vanishes, replaced by something far more ambitious, far more fun, and far more intelligent. It's a great example of how science fiction and social comedy can fuse without compromising either end of the deal.
Just the two of us
Birdy opens with two characters: the titular Birdy Cephon Altira, a sassy space cop in the "disintegrate first and ask questions never" mold; and Tsutomu, a genial high school kid whose idea of pushing the envelope is to sneak into abandoned buildings on urban spelunking missions. One night he's exploring a derelict where Birdy, now on Earth, has cornered a most-wanted cosmic criminal. Tsutomu steps in at the wrong moment, and Birdy, unable to pull a punch fast enough, accidentally kills him.
Well, not completely. Apparently there was enough of Tsutomu's body left to salvage and stick in a stasis chamber until the genetic engineers of Birdy's civilization can figure out how to reboot him. But the only way to save Tsutomu's mind was to temporarily stick it in Birdy's body — and now only one of the two can incarnate at any given time. It's either Tsutomu "piloting" the body with Birdy inside riding shotgun, or Birdy in charge, leaping across rooftops while Tsutomu inside looks on haplessly.
This is a fun premise, if not a totally original one: e.g., the riotous body-sharing comedy All Of Me, where Lily Tomlin and Steve Martin have to pull this same stunt. And for a little while, it seems like Birdy may follow the same basic pattern. These two have to learn to share the same body responsibly long enough to figure out how to untangle themselves, including problems like embarrassing bodily functions and how to deal with Tsutomu getting no sleep and missing class whenever Birdy takes off after her enemies. (And with the two of them becoming fast friends in the process, of course.)
Where Birdy ramps up, though, is in how the story isn't circumscribed by the premise. Again, it's just the starting point, and the show wastes no time demonstrating how it has larger ideas on its mind. After Tsutomu's death and resurrection, Birdy ends up stationed more or less indefinitely on earth until her supervisors can restore Tsutomu's body, and until she can close a case on Earth that has galaxy-spanning repercussions. The best part is her cover story: Birdy hides in plain sight as a pop idol, Shion Arita. Her rapacious "agent" is her alien controller, running her ragged to keep the money coming in because cover stories for alien police don't pay for themselves.
Odd couple gets even
The first half of the show deals with Birdy and Tsutomu trying to track down a kind of alien superweapon, the "Ryunka", not just because of how destructive it is but because it can be fused with a living host and thus made almost undetectable. Birdy's quest for the Ryunka potentially leads her into the same social circles as a Bill Gates-like tech genius who may have gotten to it first. This is all alongside Tsutomu's growing feelings for a girl in his class, Sayaka, whose wealth and upbringing have only left her lonely and isolated, and who hungers for friendship and connection, however she can find it.
It's not hard to figure out where the Ryunka has been hidden; the dots in this show more or less connect themselves quickly and early on. But this leads to both Tsutomu and Birdy having to make difficult and repercussive decisions: is it possible to disentangle the Ryunka from its host? And if not, do they have to level the whole planet to keep it from breaking loose and destroying everything else? The fact that there's a second half to the show is itself an answer to those questions, but the Solomonic ways they handle those questions (and the ways we get eased into confronting them in the first place) show that the people involved actually thought about what was at stake.
The second half of the show may even be better in some ways. It doesn't deal with the end of everyone's world, but an emotional apocalypse instead, something every bit as devastating to the people involved. We, and Tsutomu along with us, also see more of Birdy's past: she's essentially the product of genetic engineering to create soldiers, such that "supercop" is the only job that anyone feels comfortable giving someone like her. In the aftermath of the events that ended the first season, a cadre of alien refugees land on earth (a la the legendary never-filmed SF cult classic The Tourist), among them a figure from her own past that she still has deep and abiding feelings for, and who's made great strides at assimilating into human society. The bad news is that the weaponized side of him is taking over, and Birdy and Tsutomu have to pool what resources each of them can give to find an answer — again, while trying to balance the rest of their lives against the ticking bomb about to blow both of theirs up.
Not just a pretty face (or a powerful fist)
One hallmark of a great show, or even just a good-to-great one, is when most every salient point you could make about it is a net positive. Birdy does something few shows with a female protagonist do well: it gives us one that's appealing and attractive, but not at the expense of everything else about her. Her day job as Shion is just that, a job, one that has a lot of annoying and thankless downsides — as when, at one point, she's forced to do an autograph session that features some of Tsutomu's slobbering (male) classmates. (It's made worse by Birdy's psyche being temporarily out of commission at the time, and Tsutomu having to ape her behavior.) The world Birdy/Shion is in may treat her as cheesecake, but the show doesn't, and that makes all the difference. And while she may also be a tough cookie generally, she's not incapable of empathy and compassion; she just saves it for the people who really matter, like Tsutomu, who becomes a friend for her from the inside out (figuratively and literally).
Birdy's animation studio was A-1 Pictures (Welcome To The Space Show), and while most of the show is acceptably TV-level, it goes up anywhere from one to three notches whenever Birdy steps into action. Her fights are fantastically well-done: fluid, detailed, and in the penultimate episode, even a little experimental, as in one season-capping fight when the animators progressively trade detail of subject for fluidity and sheer energy of movement. Even many of the pedestrian scenes with her are lively and expressive, in a way that's redolent of genuine artistic effort and not just cleverness on the part of someone with a computer.
No story needs an outlandish premise to be inherently interesting; it just needs to follow through on whatever ideas it has in ways that show thought and care and invention. Some time back I watched Guilty Crown, a gorgeous-looking garbage salad of an anime with too much going on and not enough of a reason to care. Some of its elements echoed those in Birdy — e.g., a character with a double life, including a public pop-star persona — but none of them are developed intelligibly or thoughtfully, and the waste of Hiroyuki Sawano's fine soundtrack work also hurt. Birdy starts with just enough of an idea to be an attention-getter, and then goes places the idea alone can't. It's one to seek out and treasure.
Postscript: Birdy The Mighty has had multiple print runs in its life on DVD in English-speaking territories, but as of this writing all of them are now out of print and only available at inflated costs.