These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Broken Base: The anime adaptation. Some claim it to be a good anime with strong political and philosophical messages and themes along with the action. Other find it to be either So Okay, It's Average or a dark shonen Attack on Titan ripoff catered to the lolicon fanbase. And it's even more base breaking within the light novel readers, as some who read the light novel felt that the anime drastically changed many scenes or cut out a lot of content while others say that it stays true to the mood and theme of the light novels.
In the light novels, The Fugitive Arch (volumes 5 and 6). The infamous NTR where the antagonist forced a marriage into Kisara and frame Rentaro for murder and put Enju and Tina to one of the worst suffering hell (such as implications that Enju suffered physical and emotional abuse and torture by "buddy killer") has caused a lot of controversy among viewers. Some said the Fugitive arch adds a lot of Tear Jerker drama and appropriately deconstructs Rentaro's utilitarian ethics. Others find this storyarch to be Facepalm worthy feeling that the storyarch was created just to piss the readers off.
Darkness-Induced Audience Apathy: Because the light novel author has good habit of killing off a good number of characters (or at least put Rentaro and Enju through sadistic hell), many detractors claim that the author's writing is terrible because of his tendency to kill off such characters or put them through hell without fully developing such characters. Detractors accuse the author for putting too emphasis on sadistic treatment of the characters while ignoring to clear up several plot points such as Enju's high corrosion rate. Volumes 5 and 6 takes this trope Up to Eleven with the NTR plot device and put Rentaro, Enju, Tina, and Kisara into an even worse suffering hell. This caused many Chinese translators of the light novel to drop this series because of not only the sad and depressing nature of the series but also the involvement of a trollish plot device.
Draco in Leather Pants: Disturbingly, the Hiruko pair has gotten a few fan following and support. It also doesn't help to note that Kagetane's daughter, Kohina, happens to be as equally cute as the main loli, Enju Aihara.
Meanwhile in America, the Tina Sprout/Renatro shipping is preferred more than the Rentaro/Enju AND Rentaro/Kisara pairing combined.
Fandom Rivalry: Developed this with Attack on Titannote Because of the similar premise of humanity in a defensive war against a monstrous threat and No Game No Lifenote For the spot of "Best Loli of the Spring 2014" season, as both Black Bullet and No Game No Life have male protagonists with lolis as partners seen as Little Sister Heroine in the eyes of the said protagonists.
Love It or Hate It: The anime adaption itself. Some people who simply watched the first episode accused the series as being a dark shonen Lolicon pandering series while others enjoy the anime as being one of the most well-written series in the spring 2014 anime season.
It's even more polarizing among those who had read the light novel. Some light novel readers felt that the anime is really rushed and that the anime cut out or altered many of the important details and scenes from the light novel; others felt that the anime is more faithful to the light novel than the manga (as the manga is stated to end with the first volume of the light novel series).
What Do You Mean, It's Not Political?: The light novels have a lot of strong political overtones throughout the series. Namely, the status with the cursed children can easily compared to the Jim Crow segregation laws in the United States and to the apartheid government in South Africa. Should a small minority of lolis born with an incurable parasitic virus be treated as low lives in society and deserved to be lynched and murdered in public, or should they be treated as equals with normal humans? Are the cursed children by nature destined to be evil since they'll turn into Gastrea monsters anyway, or has the circumstances of society caused the cursed children into a life of poverty and crime? Are the cursed children the key to defeating the Gastrea and funding the cure to the virus? Can the cursed children and humanity alike can live together side by side in peace? Many of these points are explored throughout the novel. Seitenshi can be easily compared to Martin Luther King Jr. and Nelson Mandela for civil rights for the cursed children where she is a strong believer of pacifism and there can be nonviolent change in society to help the cursed children. Regardless, the political overtones in the light novel can be used to apply to modern Japanese society as well. note Japan is known to be a very racist society, particularly towards Koreans
Also, Black Bullet has a very strong left-leaning political view; as the main character, Rentaro, and Seitenshi want to reform society to grant civil rights to the cursed children and society to treat them with dignity and respect. The series has put a lot of emphasis and deconstructs Rentaro's utilitarianism while the antagonist are either named after libertarian philosophers such as Ayn Rand, or a secret Right Wing Militia Fanatic organization wanting to reunite Japan under their ultranationalist fist and use genetically modified Gastrea to Take Over the World.