If you're looking for manga similar to Black Bullet, you might like these titles.
Japan, Year 2X65, Tokyo. As the population continues drop due to a mysterious disease, through a certain incident, the fates of two young men, the orphan Noel, and Rikka, the heir of a distinguished Mafia family, will cross...
In a nightmarish Earth, bugs (mushi) have begun to infect humans. Though not hurting their hosts initially, eventually the mushi devour the hosts' dreams, killing them in the process. Humans that are "lucky" enough to have their mushi killed ahead of time become emotionless and thoughtless zombies. In this uncertain time the Mushibune, infected humans who resist their persecution, are up against the Special Environment Preservation Agency, an organization hell-bent on destroying the mushi. Kakkou, SEPA's top agent, has been sent undercover to track down a high school student; but he didn't realize he'd meet and fall for the lovely Shiika instead...
Many years after a devastating war, Earth is now being watched by a group of beings known as The Third, named for the third red eye on their forehead that can access various computer systems. Navigating this barren, apocalyptic landscape is Honoka, a jill-of-all-trades who uses her powers to keep her friends from The Third's deadly grasp.
In a world corroded by the Rusty Wind, a journey begins for the newly-immortal Akaboshi Bisco. Together with Milo, they arrive in Shimane. There, rumors of the "Immortal Priest" Kelshinha—said to have ruled Shimane for 200 years—reach their ears. In search of a cure for Bisco's immortality, the two infiltrate a city of turmoil, strange rituals, and gruesome sacrifices, where many religious groups dwell in a precarious balance.
It’s the year 2125, and a strange plague called “Cagaster” appears. One-in-a-thousand people is infected by this disease, which turns humans into monstrous cannibalistic insects. Two-thirds of humanity is decimated... 30 years later, young expert bug exterminator and mercenary adventurer Kidou and newfound friend Ilie struggle to survive in this brutal new world, while delving into the mysteries of the plague and its causes. Kidou is tasked with finding Ilie’s mother, after being entrusted with her by her dying father. Meanwhile, the battle continues to rage against the mutated population of Earth, with the code possibly being cracked to finally end the nightmare.
The series is set 150 years after humanity lost half of the planet due to a mysterious "black fog." To contain the "black fog," 3,000-meter-tall (about 10,000-feel-tall) walls were erected to split the world, and the half of the human population that survived now live in cities called "Arks." Shidou Enishi, one of the few Japanese survivors, runs a detective agency on the ninth ark. While pursuing a male suspect in a burglary, he learns of a massive conspiracy, one that may be tied to the Rivigarudo syndrome that is mutating its victims into something inhuman.
Ten years ago, a terrible virus swept the globe. It turned its victims into bloodthirsty monsters called Dracules, and the only cure is death. Now, with humankind on the brink of extinction, only the elite warriors of the Vius Squad stand between chaos and civilization. New recruit Leila Mikami is one of the squad's most promising young warriors, but she has another agenda: Her parents were killed by a Dracule, and she's determined to take revenge. To do this, she has to find the Dragon Eye - a magic weapon that will make her the most powerful warrior in the world.
Forced to retreat to floating cities due to an invasion of magical armored insects, humanity must now depend on Sky Wizards to battle the menace via mid-air battles. Once known as the “Black Master Swordsman,” Kanata Age is now considered a traitor and is assigned to lead an F-class of mismatched mages. Misora Whitale has all the enthusiasm to be a leader, but she's failed 100 consecutive tests. Rico Flamel is a genius sniper, but she's a little self-absorbed, and Lecty Eisenach is a candidate with all the ambition but zero confidence. It's up to Kanata Age to train the troubled trio to become accomplished Sky Wizards.
In the near future, a large portion of humanity is wiped out by a brutal, new virus that hardens the skin while dissolving internal organs. Those who aren’t immune are either severely crippled or allowed to live with cybernetically enhanced bodies. Taking advantage of a world in chaos, a paramilitary force known as the Propater topples the United Nations and seeks world domination. Elia, a young survivor searching for his mother, travels towards the Andes Mountains with an artificially intelligent combat robot. When he encounters a group of anti-Propater freedom fighters, a maelstrom of unique characters unfolds.