Black Bullet Series by Morinohon, Shiden Kanzaki

The near future. A terrible battle against a parasitic virus called "Gastrea" has been fought...and lost. Humanity is cornered and lives in despair. Rentaro and Enju face constant danger in their work as a team of specialists working for the Tendo Civil Security Agency, one of several groups dedicated to fighting Gastrea. Enju is one of the "cursed children," who survived the virus and gained superhuman powers as a result... moreThe near future. A terrible battle against a parasitic virus called "Gastrea" has been fought...and lost. Humanity is cornered and lives in despair. Rentaro and Enju face constant danger in their work as a team of specialists working for the Tendo Civil Security Agency, one of several groups dedicated to fighting Gastrea. Enju is one of the "cursed children," who survived the virus and gained superhuman powers as a result. A crazed top-hat-wearing terrorist is on the loose, but Rentaro's got his hands full just dealing with his fellow civsec agents! less

The monstrous mutants created by the Gastrea virus have driven humanity to the brink of extinction. The only thing keeping them out of Tokyo are the giant Monoliths that surround the city and the efforts of civil security officers like Rentaro and Enju. But when they accept a strange mission from the Ministry of Defense, they uncover a plot by Kagetane Hiruko that could end in the destruction of humanity!

In the near future, civsecs like Rentaro Satomi and Enju Aihara are humanity's last defense against the viral life-forms known as "Gastrea." But now they're on a different mission, this one straight from the government of Tokyo Area: Stop the rampage of Kagetane Hiruko before he destroys the entire city!

Humanity continues to fight for its right to a future. Rentaro's enemy is the sinister Kagetane Hiruko, but there's another threat-a gigantic Stage Five Gastrea that threatens to destroy everything Rentaro has worked to protect. Overwhelming odds demand unthinkable sacrifices, but sometimes even that may not be enough...