On a gloomy morning of the 21st of December, as Prime Minister Haro Takashi was about to step off his car on a normal day to the Imperial Diet, the vehicle exploded in a large fireball that shocked central Tokyo.

At the same time, an angry mob of around 15,000 rioters were making their way across Tokyo on their way towards the Imperial Palace, smashing windows and incurring public disorder along the way. At 13:00, the rioters broke in, and the 100 Imperial Guards present joined the rioters instead of arresting them. A short fire fight occured between the police force and the Imperial Guards.

Amidst the public disorder, 3 companies of men from the Imperial Guard arrived at the Imperial Diet to seize control of the building under the premise of security. By 14:30 all members of the Imperial Diet was under custody by the Imperial Guard.

War Minister Katō Tomosaburō as well as Home Minister Tokonami Takejirō manages to escape the chaos and fled to Yokohama, where the government efforts to repeal the coup d'etat would be organized, and quick, before the rebels could find out their location.

At 16:20, a group of rioters who were injured in the crossfire of the shootout at the Imperial Palace arrived at the military hospital, where all were arrested by the Kenpeitai. They turned out to be the ring leaders. Within an hour the riot was suppressed by the military police force.

At 17:15, a detachment of Imperial Guard from the 2nd Guard Brigade arrives at the Diet, led by Tanaka Giichi, former War Minister. Realizing that their struggle is hopeless and after a brief struggle, the rest of the rebellious guards in the building surrendered.

With a casualty count of nearly 400, the Incident shook Tokyo to the core. The perpetrators were identified to be a group of rebellious Army officers who were disgrunted due to recent actions by the Government, and spurring in action inspired by the supposed mutiny of the Russian Expeditionary Army. The rioters were organized by members of the Black Dragon Society, who was in contact with the Army officers.

After the incident, Tanaka Giichi, holding the most cards on the table, having control of every single armed personnel in the region, essentially bargained his way to power in the aftermath, being appointed as the new Prime Minister by the Emperor. Martial Law was declared and the Diet dissolved during the investigation process, and using his new found powers, Tanaka Giichi with the Imperial Command from a shaken Emperor set off to restructure Japan's highest order to avoid such incident from ever happening again.