"Jūyō Sankōnin Tantei" is a manga series that revolves around the investigative work of a unique detective agency specializing in solving cases involving wills, inheritances, and estate disputes. The protagonist, a sharp and resourceful detective, leads a team that includes a legal expert and a forensic specialist. Together, they tackle complex cases where greed, family secrets, and legal intricacies intertwine. Each case presents a new puzzle, often involving hidden wills, contested inheritances, or fraudulent claims, requiring the team to employ both deductive reasoning and legal acumen to uncover the truth.

The narrative is structured around episodic cases, with each arc focusing on a specific client or dispute. The detective agency is often approached by individuals who suspect foul play or deception in the handling of a deceased relative's estate. Through meticulous investigation, the team uncovers clues, interviews suspects, and navigates legal loopholes to resolve the case. The stories frequently delve into the personal lives of the clients, revealing familial tensions, long-buried secrets, and moral dilemmas.

The main characters are defined by their expertise and distinct personalities. The detective is portrayed as highly intelligent and perceptive, with a knack for unraveling complex schemes. The legal expert provides critical insights into the intricacies of inheritance law, while the forensic specialist contributes scientific analysis to support the team's findings. Their collaboration is central to the series, showcasing a balance of intellect, intuition, and technical skill.

The manga explores themes of justice, morality, and the consequences of greed, often highlighting the emotional toll of inheritance disputes on families. The cases are grounded in realistic scenarios, with a focus on the legal and ethical challenges of estate management. The series maintains a steady pace, blending suspenseful investigations with moments of character development and interpersonal dynamics. Through its engaging storytelling and well-researched legal elements, "Jūyō Sankōnin Tantei" offers a compelling exploration of the complexities surrounding wills and inheritances.