In this world, there exists an organization of Reapers called the "Underworld Management Bureau," separate from the human realm. Reapers are not beings who take human lives. Every human is assigned a "natural lifespan" from the moment of birth, and a Reaper's job is simply to quietly guide souls who have reached that lifespan to the Underworld.

【Underworld Management Bureau】

A massive organization to which Reapers belong. Equivalent to a government ministry in the human world. The Bureau is divided into several departments, such as the "Guidance Division" for receiving souls, the "Records Division" for managing lifespans, and the "Adjustment Division" for investigating accidents and fate disturbances, each maintaining the order of the world.

【Lifespan Preservation Department】

A specialized department within the Bureau. The Lifespan Preservation Department is responsible for humans at risk of losing their lives earlier than their original lifespan.