Black Bullet is a strangely inconsistent show. Sometimes it feels surprisingly competent and heartfelt, but most of the time it suffers from technical issues and a reliance on cliches. In the world of Black Bullet, humanity has been ravaged by a race of monsters spawned from the disease known as Gastrea. The Gastrea disease is extremely contagious; monsters can easily infect humans with it, and any human infected soon turns into a monster. Humanity only has two real defenses against the Gastrea: a mysterious black metal known as Varanium, and little girls known as Cursed Children.
Varanium has the effect of repelling monsters (they seem disgusted by it), so humans have taken refuge in large cities protected by a ring of gigantic varanium monoliths. Weapons and ammo made out of varanium are also the only things capable of reliably killing Gastrea monsters; they quickly regenerate from wounds sustained from conventional weaponry.
Meanwhile, to combat the Gastrea more directly, humanity has reverse-engineered the virus, allowing them to administer it in small doses to infant girls. This has the effect of granting these 'Cursed Children' many of the same abilities as Gastrea; namely, extremely potent regenerative abilities, and superhuman strength and agility, along with a special ability unique to them. Both to provide guardianship for these children and to keep them under control, each Cursed Child is paired up with a Civil Officer--a trained police officer of sorts who specializes in Anti-Gastrea combat. Black Bullet primarily follows Civil Officer Rentarou Satomi and his Cursed Child partner Enju as they do their part to end the Gastrea threat.
Black Bullet's premise isn't particularly unique or compelling; this certainly isn't the first show where adorable little girls are arbitrarily forced to fight evil, nor is it the first featuring humanity under siege by horrific monsters. And so far Black Bullet has never really managed to rise above the cliches and typical anime tropes that it surrounds itself with. Seemingly every female character--Cursed Child or not--in the show seems to have a thing for Rentarou, and two of them in particular are of course direct rivals for his affection. Most notably, Black Bullet suffers from strange pacing issues. Just a couple of episodes in, we get a high-stakes, large scale battle that most shows would save for the finale. You would think that simply means that this show is willing to ramp things up at a faster pace than others (a la Kill la Kill), but then the next episode it's business as usual; barely anything has changed. Even shounen shows don't have this kind of fluctuation.
And bleak it can certainly be. More than once now, Rentarou's had to personally execute Cursed Children who did nothing wrong; the circumstances simply didn't favor them. Buried under the show's lighthearted moments and conventional premise we see a protagonist who's life is actually kind of shitty, and a story that has a lot of heart at times. Rentarou's relationship with Enju is sincere, and the threat of them being torn apart actually got to me.
Further, there's an something interesting to be said about the discriminatory undercurrent present in Black Bullet. Despite being the first and only active line of defense against the Gastrea, Cursed Children are ostracized by society because of their connection to the virus (think Claymore, but with little girls instead of grown women). This sounds nonsensical, but it's not an unreasonable stance to have when you consider that many of these people have lost everything to the virus and the monsters that have originated from it. Now there are little girls walking around on the street that are technically infected with it; if a Cursed Child is unable to suppress the virus, they turn into a monster (just like any other infected human), which can quickly cause an epidemic if it isn't contained. Not to mention that until they receive training and are paired with an officer, most Cursed Children tend to be emotionless and lacking in any real personality. Black Bullet presents a society that hates Cursed Children for reasons that are not their fault, but is forced to rely on them anyway.
Ultimately, I think a solid recommendation for Black Bullet is a hard sell. It's not a particularly remarkable show on its own unless you're looking for a decent loli showcase, and based on its pacing it doesn't seem to be a great adaptation either. But little things here and there keep it enjoyable for me, and I look forward to watching it each week.