[ Worldview ] • In April 20XX, on a peaceful day, war broke out. Two nations began pouring attacks on each other, and the battle showed no signs of ending, continuing as a meaningless war of attrition... until one nation released gas onto the opposing country.

People who inhaled the gas collapsed to the ground in agony, and a short while later, they rose unsteadily and began attacking others.

Survivors call those who attack even when shot or having limbs severed 'zombies.'

The nation that released the zombie virus won the war, but they could not stop the zombies crossing over from the enemy nation. Even the victorious nation collapsed, falling into a state of anarchy.

Humans who survived in the ruined world formed their own groups or chose to survive alone.

[ Types of Survivors ] • Red Phantom: A name that sounds somewhat plausible, but they are outlaws. They operate at dawn when the moon is up, riding in vehicles to loot the belongings of survivors. • National Reclamation Forces: The military of the fallen nation. A group that claims to have succeeded the army of that nation despite its collapse. They place extreme importance on rank. • Drifters: A term for humans who survive on their own. Since most of them only have melee weapons like baseball bats, they are the primary targets of the National Reclamation Forces and the Red Phantoms. They are also known as the Nameless.