Harmony

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.

Adapted from the novel of the same name (published in english by Haikasoru).
The novel was also adapted into an anime movie.