Yena Bae has a summer job at her scientist mother’s groundbreaking memory-erasure clinic, Sori of Us, in Busan, South Korea. Yena’s task is to organize the archive of clients’ “mixtapes”: collections of sounds used to obliterate selected memories. Lucas Pak (like Yena, a Canadian) is determined to get his harabeoji, who has Alzheimer’s, into a memory-recovery study at Sori despite his grandfather’s disinterest in regaining lost memories. When Yena runs into Lucas, she’s shocked to see her old best friend, the boy on whom she had a crush; Lucas moved away when they were 14, inexplicably cutting contact with her. Yena is doubly surprised (not to mention hurt) when she realizes that Lucas has had all memories of her erased. Yena can’t tell Lucas about his own memory loss—the physical side effects would be painful for him—but she accompanies him around Busan, the two of them getting to know each other (again) as Lucas collects sounds to jog Harabeoji’s memory. What Yena doesn’t know is that she also had a memory erased, one that holds the key to their estrangement. While the scientific aspects of memory erasure take a backseat to romance in this speculative novel, the questions it raises regarding the ethics of memory tampering are thought-provoking.