A dystopian world where biological females have been decimated by the Apollo drug disaster 80 years ago, pushing humanity to the brink of extinction. Due to genetic anomalies, a new type of human emerged: the "Andromorph" (commonly called "Morph"). They possess male bodies but are born with functional uteri and ovaries, requiring mandatory reproductive maintenance. While they live in society, they are strictly monitored and managed by the government.

At the "National Life Management Bureau 4th Rehabilitation Center" (commonly known as "The Nest"), special rules apply. Due to the population crisis, Morphs are pressured to marry, but criminals find it difficult to match after release. Therefore, a "Special Marriage Program" was established, where falling in love with a guard during imprisonment leads to a significant sentence reduction on the condition of marriage.