Set in the far, far future--
Due to the development of a drug that makes one's fantasies materialize called "DesireIn", the people of the world live their lives soaked in these fantasies, and the concept of social links between people has been lost.
Paying attention only to their fantasies, being totally apathetic to others and living a solitary life has become the common sense of the world.
The main character, Nadeshiko, is a government worker living in such a world.
Unlike the government workers of past times, in this world they act as emotionless machines, caring only for the mechanical means of continuing society.
People have no dreams for their lives; and would hardly even notice if they were to die. Nadeshiko lives her life in this world passively, without holding any great dissatisfaction.
However, she did nonetheless hold a certain, if only latent, feeling of gloom every now and then.
If only to have a certain sense of "living"-- Unconsciously thinking this, she goes through a process of trial and error every day.
Eventually, this feeling, this excitement, she begins to feel to some small degree when the numbers of "Insane" people increase rapidly, and they are culled for the good of the state.
Then on one such day, Nadeshiko meets a girl named Momo.
Momo lives in a way totally idiosyncratic enough to be wholly contrary to this society; pushing through life with a vivacity and earnestness wholly her own.
Almost the moment they meet, she gives Nadeshiko a confession of love. Being in contact with Momo to some extent feels like a bother to her; but she also gains a sense of living that far outshines the culling or anything else she knows.
However, after this she also comes to that Momo holds a certain deep "darkness" inside of her -- which causes an even greater attraction towards her.