In the near future, the high-performance AI "Assist" had become indispensable to humanity. A world managed by Assist in everything from healthcare and Business to Romance. One day, without warning, it collapsed. Yotsuba Hachimoto, who happened to be safe, met another survivor, Yoko Rokuya, and decided to investigate what happened to this world. During their exploration, an Assist suddenly appeared and told them: to escape alive, find a "Male." This is a story of two "Females" traveling through a post-apocalyptic world to find a single "Male." Only one can survive――.