In 2019, a rebellion broke out in the USA, sparking a global nuclear war that devastated humanity in an event known as "The Maelström." After half a century, the World Health Organization (WHO) rose to power, using advanced medical technology, nanomachines, and augmented reality to rebuild society and guarantee a better life for all. Miach Mihie, a high school student, feels that Japanese society has become too kind, and decides to rebel against their dehumanizing values. Along with two friends, Tuan Kirie and Cian Reikadou, Miach plans to end her life before the government's surveillance system, WatchMe, activates upon her 18th birthday. However, Cian reveals their plan, and only Tuan survives the suicide attempt, while Miach is presumed dead. Years later, Tuan has become a senior inspector with Helix, a WHO-affiliated organization that monitors military conflicts. After being exposed for drug-smuggling during the Niger warzone conflict by her colleague, Oscar Stauffenberg, Tuan is sent back to Japan. She arrives to find that thousands of people have committed suicide simultaneously, and she must uncover the terrorist group responsible for the unprecedented attack.