Detective Gregory Smith is a middle-aged or older supporting character in the Inazuma Eleven series, recognizable by his brown hair, grey beard, and signature detective attire. His journey into law enforcement is deeply personal; as a young man and a devoted fan of the original Inazuma Eleven team, he was profoundly affected by the bus accident that led to the team's disappearance and the forfeiture of their final match. The lack of clear answers surrounding that tragic event directly inspired his career choice, as he was determined to uncover the truth himself. This passion for the sport and its history remains a core part of his identity; despite admitting he is not an expert player, his love for football is what drives his sense of justice.

In his professional life, Gregory Smith is characterized by a dual nature. Towards the criminal elements he investigates, he is stern and uncompromising, displaying zero tolerance for those who would corrupt or harm the world of football. However, towards the young players of Raimon Junior High and other well-meaning individuals, he reveals a generous and supportive side, acting as a helpful ally and source of wisdom. Throughout the series, his primary role is that of an investigator working behind the scenes to expose the machinations of the recurring antagonist Ray Dark. He is a persistent figure in the pursuit of justice, responsible for arresting Ray Dark on multiple occasions. His investigation expands to include other threats, such as when he worked to uncover the plot of Zoolan Rice on Liocott Island.

Detective Smith develops key relationships with several main characters. He takes a special interest in Mark Evans, the grandson of Daisuke Endou, the legendary captain of the original Inazuma Eleven team. He provides crucial information to Mark about the past, revealing the details of the bus accident that ended his grandfather's career. His knowledge also proves vital during the alien incident, where he is able to explain that he had been secretly assisting Axel Blaze, protecting his sister Julia from being kidnapped. On another occasion, his timely arrival helps to rescue Jude Sharp from a sinking ship. Through his years of investigation, he also becomes a confidant of the original team's coach and a figure familiar with the history of Raimon.

Over the course of the narrative, Detective Smith's character is defined by his unwavering persistence. He does not undergo a dramatic personality shift but rather fulfills a consistent and crucial function as a protector of the sport's integrity from the shadows. His dedication is physical as well as intellectual; he willingly puts himself in danger, once being attacked and sustaining injuries while continuing his pursuit of a suspect. His notable abilities lie in his sharp investigative mind and deductive skills. Within the context of the video games, his capabilities are reflected in statistics that highlight high levels of intelligence and agility, and his character is classified with the Fire element. He continues to offer challenges to the player in post-game content, showing his enduring connection to the world of football.