Natsuki has never felt that she fits in with her neglectful family and modern Japanese society. As a child who is sexually abused by her teacher, her only friend is a plush toy hedgehog named Piyyut, who tells her he's an alien. On family vacations to her grandparents' home over the years, she falls in love with her cousin, Yuu, who also claims to be an alien. But after being caught having sex, they are torn apart. Years pass and Natsuki marries an asexual man, Tomoya, who she does not love but who shares her view of society as a factory. Natsuki, Tomoya, and Yuu eventually unite in their belief they are aliens with horrific results.
