In this world, separate from the human realm, there exists an organization of Reapers called the "Underworld Management Bureau." Reapers are not beings who steal human lives. Every human is assigned an "original 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 distortions of fate, each maintaining the order of the world.

【Lifespan Preservation Department】

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