Somewhere in Vladivostok, Russia, a deal has been successfully completed. Danger looms over the horizon; a deadly virus—capable of killing within three hours of infection—has now fallen into the hands of a mysterious woman named Maya.

Enter Fujimaru Takagi, a seemingly ordinary student at Mishiro Academy in Japan. However, very few know that he was famed for exposing crimes and corruption of high-profile individuals with his brilliant hacking powers—the infamous "Falcon" who had abruptly vanished from the cyberworld. Only members of Third-I, a top-secret division of the Public Security Intelligence Agency led by Fujimaru's father, Ryunosuke, and his friend Otoya Kujou know of his past.

When a KGB agent is murdered in Japan, the only clue to his death is a memory chip found at the scene of the crime. Fujimaru is recruited by Third-I to decode the chip, which contains a video file of an event called the "Christmas Massacre." Investigating the incident further, Fujimaru's father uncovers more information about the homicide and a mysterious code, "Bloody Monday," before being framed for the murder of his superior. Now, it is up to the hacker Fujimaru to utilize his expertise to help Third-I prevent the spread of terror and destruction in Japan, while attempting to clear his father's name.

Bloody Monday was published in English by Kodansha Comics USA from August 23, 2011, to July 23, 2013. It was also released in Italian by Edizioni Star Comics from March 14, 2010, to November 12, 2011.

The series was adapted into a Japanese live-action television show that aired from October 11, 2008, to December 20, 2008. A second season aired from January 23, 2010, to March 20, 2010.