Yukihira Natsumi is a no-nonsense, intelligent Tokyo homicide cop known as the department's "number one" case closer, who nevertheless also has a bad reputation for not working well with others and pushing the limits of the law. As she sees it, her only job is bringing in the bad guys, and the results are all that counts. However, she is haunted by a hostage case five years prior in which she had to pull her weapon and kill a man, which earned the ire and distrust of some of her coworkers and members of the community. To bring balance to her life, Natsumi must find a way to deal with her demanding work, the aftermath of a divorce, and caring for her young daughter—all while chasing down a serial killer who's taunting the police with serialized short stories that foretell the next murder with no time to spare.