John Rain is an assassin for hire, specializing in deaths that appear natural, who operates in the shadows of Tokyo's criminal underworld. Barry Eisler's thriller series follows this half-Japanese, half-American killer through assignments that entangle him with yakuza, intelligence agencies, and his own complicated past. Rain is a connoisseur of Japanese culture, a jazz lover, and a loner who trusts almost no one, characteristics that make him both effective at his work and isolated from ordinary life. Eisler, himself a former CIA officer who lived in Japan, brings authenticity to both the tradecraft and the Tokyo settings. The novels feature detailed descriptions of surveillance, countersurveillance, and the various methods Rain employs to kill without leaving evidence of murder. They also explore the neighborhoods, bars, and hot springs of Japan with evident affection. The series examines questions about morality and violence: Rain has a code, refusing certain contracts and showing mercy when he can, but he remains a killer. The books follow him through attempts to leave the life, relationships that challenge his isolation, and the consequences of choices made across multiple novels. Readers who enjoy espionage thrillers with strong sense of place and moral complexity will find the Rain series satisfying.