In the year 1923, a vampire crisis takes Tokyo by storm. Provoked by the illegal trade of Ascra, an artificial blood source, the population of vampires begins to rapidly increase within the city. Under orders from Lieutenant General Sounosuke Nakajima, the Special Forces Unit 16 gathers vampires within the military to create a new undercover vampire-hunting unit known as Code Zero. Leading the unit is Colonel Yoshinobu Maeda. Responsible for locating the source of the Ascra trade as well as capturing and killing vampires, he is pressured into producing fruitful results amidst the growing criticism that threatens to decommission the unit. To make matters worse, the vampires within the unit are struggling to grasp their newfound powers and identities now that they are no longer human. With the world at odds against them, the members of Code Zero must find a way to curb the crisis or otherwise fall victim to their own demonic natures.

After her parents were brutally murdered, school girl Sawa was taken into custody by Akai and Kanie, a pair of detectives assigned to her case. Corrupt and immoral, they train the girl to become a weapon, dangling the promise of vengeance in front of the hapless orphan. From celebrities and politicians to influential businessmen, Sawa is tasked with assassinating targets selected arbitrarily by her crooked overseers. She executes every mission without fail, and her distinctive weapon has become infamous among the city's police officers. Physically abused by Akai, who is no more righteous than her victims, Sawa begins to dream of a life unhindered by the shadow of her guardians. One day, Sawa meets Oburi, a fellow orphan and vigilante. They quickly form a bond born of desperation and disgruntlement at the unjust world, envisioning a future free from the stain of murder.

Red panda Retsuko, worked to the bone, unleashes her frustration in the form of death metal. Lately, though, she's found another joy—getting the most likes possible on her Instagram posts. In fact, it is said that social media attention can release endorphins. As Christmas falls upon the city, Retsuko's hunger for validation only grows, pushing her to find new ways to embellish and sugarcoat her otherwise drab life for the internet to see.

The bullies at Yoo Hobin's high school are no ordinary trouble-makers: they are NewTubers, budding internet celebrities who force Hobin to partake in humiliating videos and host live-streams in his house. Hobin only manages to stay strong by reminding himself that he needs to work hard to support his hospitalized mother. However, during his classmate Woo Jihyeok's live stream, Hobin completely snaps after a humiliating incident. As a result, the two men engage in a grotesque fistfight that lasts until dawn. The following day, Hobin discovers that the livestream of his fight went viral on NewTube, turning him into a celebrity overnight. After he realizes that making viral videos is a very lucrative endeavor, Hobin agrees to team up with Jihyeok to create a channel that features his martial prowess. However, Hobin needs to become a seasoned fighter and keep his distance from those who seek to use him for his newfound fame, unless he wants a lack of views to become the least of his problems. Thankfully for him, the unexpected discovery of a series of obscure self-learning videos might be just what he needs to survive in the content creation industry.