In Japan, a covert industry has grown up around the "wakaresaseya" (literally "breaker-upper"), a person hired by one spouse to seduce the other in order to gain the advantage in divorce proceedings. When Satō hires Kaitarō, a wakaresaseya agent, to have an affair with his wife, Rina, he assumes it will be an easy case. But Satō has never truly understood Rina or her desires, and Kaitarō's job is to do exactly that --- until he does it too well. While Rina remains ignorant of the circumstances that brought them together, she and Kaitarō fall in a desperate, singular love, setting in motion a series of violent acts that will forever haunt her daughter's life.