High school student Arashi Mikami is a member of a secret group of assassins, who aren’t the typical for hire sort. Under the leadership of the Mochizuki General Hospital’s chairman, Masamune Mochizuki, the team consists of a handful of hospital staff members and a couple other teenagers. Their purpose is to remove the “cancers” of society by performing triage on individuals given a black label. Evil will be excised from the world before its wickedness spreads.
Arashi Mikami isn't the average teenage boy. His tragic past has led him to his first mission for Black Label and he plans to excise the "cancers" of society with them.
Arashi is now a full-fledged member of Black Label. His team’s first mission is to hunt down Jin Masaki, who managed to escape their grasp previously.
While on a mission Mikoto and Arashi find that someone else has beaten them to their targets. Could this mysterious new woman be an ally or will she receive a Black Label too?
Mikoto heads out on a rescue mission that ends up putting her against overwhelming odds. Will she become a casualty or can she overcome the odds?
Oriha’s celebrating the opening of a new TV studio, only for it to be taken over. The assailants aren’t afraid of shedding blood, or making it clear who they’re gunning for.
The studio is under siege and this group seems all too intent on showy murder. Oriha suspects the true nature of this assault, but she’s in some serious trouble.
The studio was a diversion from the arrival of a new drug with side effects unknown even to its distributors. Black Label’s leader has an intrinsic link to it, as does Arashi.
Hitsugi is attacking other members of Black Label while in a strange fugue state. Yuko knows why and decides to fight at full strength, but Arashi still trusts Hitsugi.
A detective has gone missing. Black Label goes in to rescue her, and Hitsugi once more faces the twins of Syringe, hoping to settle things.
The women of Black Label discuss what they know so far. However, the organization’s job isn’t complete, and Arashi heads out with Mikoto to acquire more information.