In the future, Utopia has finally been achieved thanks to medical nanotechnology and a powerful ethic of social welfare and mutual consideration. This perfect world isn't that perfect though, and three young girls stand up to totalitarian kindness and super-medicine by attempting suicide via starvation. It doesn't work, but one of the girls—Tuan Kirie—grows up to be a member of the World Health Organization. As a crisis threatens the harmony of the new world, Tuan rediscovers another member of her suicide pact, and together they must help save the planet...from itself.

In 2019, following an uprising in the USA and a subsequent global nuclear war, humanity was decimated by a catastrophe called "The Maelström." A half-century after this cataclysmic event—to preserve humankind—the World Health Organization (WHO) has progressively assimilated worldwide political power and completely redefined society: people are now considered public resources and are guaranteed a happier life. The heightened development of medicine, nanomachine technology, and augmented reality promote this greater devotion to human health. Suffocated by the excessive kindness of Japanese society, high school student Miach Mihie decides to oppose the societal values she considers dehumanizing before the health implant surveillance system WatchMe activates itself the day she turns 18. Miach plans to kill herself with two of her friends, Tuan Kirie and Cian Reikadou. However, Cian betrays the pact in disagreement with Miach's intentions, allowing Tuan to survive her suicide attempt, unlike Miach, who is declared dead. Thirteen years later, now a high-ranking inspector of Helix—an organization affiliated with WHO to monitor military conflicts—Tuan is sent back to Japan after her drug smuggling activities in the Niger warzone are discovered by senior Helix inspector Oscar Stauffenberg. On her first day back to the country she tried running away from, thousands of people simultaneously commit suicide. Tuan is now in charge of investigating this wave of mass suicide and exposing the terrorist organization behind the unprecedented attack.

Haruta and Chika are members of their high school wind instrument club that is on the verge of being shut down. The two are childhood friends, and they spend their days practicing hard while also trying to recruit new members. When a certain incident happens within their school, they work together to solve it.

One rainy day, Akane crosses path with a kind young man who tacitly offers to her his coat. On their second encounter, he confesses that he doesn't know who he is, his name or his past, but feels contented by just being with her. Besotted, Akane sets out to find his name, and to unravel his enigmatic connection with a famous cursed dance rumoured to kill anyone who attempts to perform it.