Amane is ten years old when she discovers she's not like everyone else. Her school friends were all conceived the normal way, by artificial insemination, and raised in the normal way, by parents in 'clean', sexless marriages. But Amane's parents committed the ultimate taboo: they fell in love, had sex and procreated.

As Amane grows up and enters adulthood, she does her best to fit in and live her life like the rest of society: cultivating intense relationships with anime characters, and limiting herself to extra-marital sex, as is the norm. Still, she can't help questioning what sex and marriage are for. But when Amane and her husband hear about Eden, an experimental town where residents are selected at random to be artificially inseminated en masse (including men who are fitted with artificial wombs), the family unit does not exist and children are raised collectively and anonymously, they decide to try living there.