"Deka Wanko" centers on the life of Aoi Nogami, a young police officer with an extraordinary ability to communicate with dogs. This unique skill allows her to solve crimes and uncover hidden truths that would otherwise remain undiscovered. Aoi works alongside her canine partner, a highly intelligent and loyal German Shepherd named Max, who plays a crucial role in their investigations. Together, they form an unconventional but effective crime-solving duo within the police force.

The narrative unfolds in a bustling urban setting, where Aoi and Max tackle a variety of cases ranging from petty thefts to complex homicides. Aoi's ability to understand and interpret the thoughts and behaviors of dogs often provides critical insights that human investigators overlook. This dynamic creates a blend of procedural crime-solving and lighthearted moments, as Aoi navigates the challenges of her job while balancing her personal life.

Supporting characters include Aoi's colleagues, who range from skeptical to supportive of her methods, and a recurring antagonist who challenges her abilities and motives. The series explores themes of trust, teamwork, and the bond between humans and animals, often highlighting the emotional depth of these relationships. Each case serves as a self-contained story arc, contributing to the overarching development of Aoi's character and her growing reputation within the police department.

The manga balances episodic crime-solving with a gradual progression of Aoi's personal journey, including her struggles to gain acceptance in a male-dominated profession and her efforts to prove the value of her unconventional approach. The interplay between Aoi and Max remains a central focus, with their partnership evolving as they face increasingly complex and dangerous situations. The series maintains a steady pace, blending suspense, humor, and heartfelt moments to create an engaging narrative.