Cloud Atlas

Tribesman Zachry Bailey recounts stories to his grandchildren on an extraterrestrial Earth colony.
Pacific Islands, 1849[edit]
Adam Ewing, an American lawyer, has come to the Chatham Islands to conclude a business arrangement with Reverend Horrox and his father-in-law. In Horrox's plantation, he witnesses the whipping of a Moriori slave, Autua, who later stows away on the ship. Autua confronts Ewing and convinces him to advocate for Autua to join the crew as a free man. Dr Henry Goose slowly poisons Ewing, claiming it is the cure for a parasitic worm, to steal Ewing's valuables. As Goose administers the fatal dose, Autua saves Ewing. Returning to the United States, Ewing and his wife Tilda denounce her father's complicity in slavery and leave to join the abolition movement.
Cambridge/Edinburgh, 1936[edit]
Robert Frobisher, a young English composer, finds work as an amanuensis to aging composer Vyvyan Ayrs, allowing Frobisher the time and inspiration to compose his own masterpiece, "The Cloud Atlas Sextet". Frobisher begins reading Ewing's journal, which he has found with the latter portion missing, among the books at Ayrs's mansion. Ayrs demands credit for "The Cloud Atlas Sextet" and threatens to expose Frobisher's homosexuality if he refuses. Frobisher shoots Ayrs and flees to a hotel, where he uses the name Ewing. He finishes "The Cloud Atlas Sextet" and commits suicide with a gun just before his lover Rufus Sixsmith arrives.
San Francisco, 1973[edit]
Journalist Luisa Rey meets an older Rufus Sixsmith, now a nuclear physicist. Sixsmith tips off Rey to a conspiracy regarding the safety of a new nuclear reactor run by Lloyd Hooks, but is killed by Hooks's hitman, Bill Smoke, before he can give her a report that proves it. Rey finds Frobisher's letters to Sixsmith and tracks down a vinyl recording of Frobisher's "Cloud Atlas Sextet". Isaac Sachs, another scientist at the power plant, passes her a copy of Sixsmith's report. Smoke kills Sachs by blowing up his plane and runs Rey's car off a bridge. She escapes but the report is destroyed. With help from the plant's head of security, Joe Napier, Rey evades another attempt on her life, which results in Smoke's death. With another copy of the report obtained from Sixsmith's niece, she exposes the plot to use a nuclear accident for the benefit of oil company executives, who are indicted as a result.
London, 2012[edit]
Sixty-five-year-old publisher Timothy Cavendish reaps a windfall when Dermot Hoggins, the gangster author of Knuckle Sandwich, murders a critic who gave the novel a harsh review, generating huge sales. When Hoggins's brothers threaten Cavendish's life for Hoggins's share of the profits, Cavendish asks for help from his wealthy brother, Denholme, who tells him to hide at Aurora House. On the way there, Cavendish reads a manuscript of a novel based on Luisa Rey's story, and recalls his relationship with a woman named Ursula. He visits the house where she lived with her parents and discovers that she still lives there. Believing Aurora House is a hotel, Timothy signs papers "voluntarily" committing himself; in fact, Aurora House is a nursing home (in Ayrs's old mansion). Denholme reveals to Timothy that he sent him there as revenge for Timothy's affair with Denholme's wife Georgette. The head nurse, Noakes, is abusive, and contact with the outside world is denied. Cavendish escapes with three other residents. He resumes his relationship with Ursula and writes a screenplay of his experience.
Neo Seoul, 2144[edit]
Sonmi-451 is a "fabricant", a human cloned for slave labor, living as a server at a fast food restaurant in a dystopian South Korea. She is exposed to ideas of rebellion by another fabricant and friend, Yoona-939. After witnessing Yoona being killed for rebelling, Sonmi is rescued from captivity by Commander Hae-Joo Chang, a rebel. He exposes Sonmi to the larger world, including the banned writings of Aleksandr Solzhenitsyn and a film version of Timothy Cavendish's "ghastly ordeal". They are found and Sonmi is captured. Hae-Joo rescues her, introduces her to the leader of the rebel movement, and shows her that clones are not freed at the end of their contract but killed and recycled into food for other clones. Sonmi makes a public broadcast of her story and manifesto. The authorities intervene to halt the broadcast; Hae-Joo is killed in the firefight and Sonmi is recaptured. After recounting her story to an archivist, she is executed.
Big Isle (Hawaii), 106 winters after the Fall (2321)[edit]
Zachry Bailey lives in a primitive post-apocalyptic society called the Valley on the Big Island of Hawaii.[13] The Valley tribesmen worship Sonmi-451; their sacred text is taken from the broadcast of her manifesto. Zachry is plagued by visions of a demonic figure called Old Georgie, who urges him to give in to his fears. Zachry, his brother-in-law Adam, and his nephew are attacked by the cannibalistic Kona tribe. Zachry runs into hiding and his companions are murdered. His village is visited by Meronym, a member of the Prescients, an advanced society using the last remnants of high technology. Meronym's mission is to find a remote communication station on Mauna Sol and send a message to Earth's off-world colonies. Catkin, Zachry's niece, falls sick, and in exchange for saving her, Zachry agrees to guide Meronym to the station, where Meronym reveals the true story of Sonmi-451. Returning, Zachry finds his tribe slaughtered by the Kona. He kills the sleeping Kona chief and rescues Catkin, and Meronym saves them both from the returning Kona and is in turn saved by Zachry. Zachry and Catkin join Meronym and the Prescients as their ship leaves Big Island.

Question: What is the relationship between Somni-451 and Yoona-939?
Answer: friends