At the end of the 21st century, the earth experienced the Third World War. The war accelerated the melting of polar glaciers, and the rise of sea levels caused the earth's land area to greatly shrink. Coastal cities and countries on every continent were submerged, and residents were forced to emigrate.
After several years of recovery, Europe lost control and faced a sharp reduction in land area. Africa rose up and broke away from the suppression of all parties. As a result, the tripartite structure of the United States of America, the United States of Asia and Europe, and the United States of Africa was formed in the early 22nd century.
Except for the coastal countries that have disappeared, the other countries controlled by the three coalition governments continue to have 21st century names. The internal governance and control of the country under the coalition government are independent of each other, but are subject to the security regulations of each coalition government.
Each coalition government uses a unified currency, and the world's common currency uses gold currency issued by the World Federation Bureau.
Against this background, a telephone service agency located in Will City, Country Z, received an unexpected visitor.
Purpose: When alternative immortality technology becomes a reality, will we still be the same?