"Tantei Team KZ Jiken Note" centers around a group of middle school students who form a detective team to solve various mysteries and incidents in their daily lives. The protagonist, Aya Tachibana, is a reserved and observant girl who struggles with self-confidence. She becomes involved with a group of boys—Kazunori "Kaz" Tokiwa, Takakazu "Tak" Yano, Wataru "Wacchan" Akiyama, and Kei "Keippi" Tsuchiya—each possessing unique skills and personalities. Kaz is the charismatic leader with a sharp mind, Tak excels in physical strength and combat, Wataru is tech-savvy and resourceful, and Kei has a knack for gathering information and social connections.

The narrative unfolds as the team takes on cases ranging from school-related mysteries to personal dilemmas faced by their peers. Their investigations often involve uncovering hidden truths, solving puzzles, and navigating interpersonal conflicts. The series emphasizes teamwork, problem-solving, and the importance of understanding others' perspectives. While the cases are relatively lighthearted and grounded in everyday life, they often carry underlying themes of friendship, trust, and personal growth.

Aya's development is a central focus, as she gradually gains confidence through her involvement with the team and her contributions to solving cases. The dynamic between the members highlights their individual strengths and how they complement each other, creating a cohesive unit. The series balances mystery-solving with moments of humor and camaraderie, making it accessible to a younger audience while maintaining a sense of intrigue and engagement.