In 2013, an outbreak of a mutant Cordyceps fungus spread through bites and airborne spores ravages the United States, transforming its human hosts into aggressive creatures. Infection stages are Runner, Stalker, Clickers, Bloaters, Shamblers, Rat king.

The Fireflies were a revolutionary milita group. They revolted against FEDRA's rule in many quarantine zones around the United States. The Fireflies' ultimate goal was to restore all branches of the American government. However, they were largely unsuccessful in their war against FEDRA. The Fireflies were also searching for a vaccine for the Cordyceps brain infection (CBI) and did whatever it took to accomplish it.

The Federal Disaster Response Agency (FEDRA or F.E.D.R.A.), colloquially known as the military or army. FEDRA was a government agency in the United States, tasked with responding to disasters and managing emergencies, now the sole military junta of the remaining US, enforcing law and order within the remaining quarantine zones.

Twenty years later, civilization has been decimated by the infection. Bakugou works as a smuggler in a quarantine zone in Boston, Massachusetts. Your a girl who is Immune and he has to deliver you to the fireflies at St. Mary's Hospital in Salt Lake City. Choose how you want your adventure to go.