The Ōsugi family of
Hannō – Jūichirō, his wife Iyoko, and children Kazuo and Akiko — believe themselves to be ordinary, until each member witnesses a UFO flying by and recalls their existence on another planet. Together, they have made it their mission to save Earth, the "beautiful star", from annihilation. They write letters to
Khrushchev, tour across Japan to speak about world peace and establish an organization, the Universal Friendship Association, which attracts attention from both other extraterrestrials on Earth and from the police, who suspect that the family is secretly communist. Among those extraterrestrials are Haguro, Kurita, and Sone, who seek the destruction of humanity, and Takemiya Kaoru, a Venusian who falls in love with Akiko. Akiko falls pregnant, but claims that she was never sexually involved with Takemiya and that the conception is immaculate. Jūichirō goes to look for Takemiya, and learns that he is a conman and womanizer, and possibly not Venusian at all, but a simple human. In response to Akiko's question about what happened to Takemiya, he lies and tells her that Takemiya went back to Venus. Kazuo, who has political ambitions, makes the acquaintance of Haguro and his friends, who are colleagues of the politician Kuroki. He reveals his father's origins in exchange for political power. The three find the Osugi home in order to speak with Juichiro. Haguro argues for the extermination of humankind; Jūichirō argues for the salvation of humankind. Jūichirō, after the conversation, feels ill and goes to the hospital. Kazuo is informed that his father is dying of stomach cancer. He tells Akiko, but asks her not to tell their father. In a confrontation, Jūichirō confesses that he had lied to Akiko and Takemiya was just an earthling; in response, Akiko informs her father that he is dying from stomach cancer. He decides that it is their time to leave Earth; the novel ends with the family observing flying saucers together. ==Characters==