Kaoru Ichijo is a police inspector and a central figure in the fight against the Gurongi, serving as the primary operative of the special Science Police force formed to combat these monsters. He is born on April 18, 1974. His background is deeply shaped by a personal tragedy: on his tenth birthday, his father, also a policeman, drowned while attempting to rescue people from a swollen river. This event instills in Ichijo a profound sense of duty and a desire to follow his father's example of selfless service. As an adult, he maintains a tradition of returning to his hometown to visit his mother, who works as a nurse, on his birthday.

In terms of personality, Ichijo is the picture of a dedicated and hardworking officer. He is described as having a serious, often stern appearance, and he smiles very rarely, which makes his occasional smiles notable to those around him. He is strict with himself and places his professional responsibilities above his personal life, almost always being engrossed in his work. Despite this severity, he possesses a friendly and insightful nature, and is fundamentally a model policeman who firmly believes in doing the right thing.

His core motivation stems from this powerful sense of duty. He feels a strong obligation to protect citizens and to bring criminals to justice, a job he believes should be handled by the police without involving civilians. This belief initially puts him at odds with the situation, as he finds the fight against the Gurongi is being led by Yusuke Godai, an ordinary civilian who is not bound by police regulations. However, witnessing Yusuke’s unwavering conviction and heroism leads Ichijo to change his perspective. He comes to accept that Yusuke’s way is the most effective method to protect people, and from that point forward, his motivation shifts to providing Yusuke with unwavering, and at times rule-bending, support.

Within the story, Ichijo acts as Yusuke Godai’s most trusted ally and partner. While Yusuke transforms into Kamen Rider Kuuga to fight physically, Ichijo handles the behind-the-scenes operations, forensic research, and logistical support. He provides Yusuke with essential equipment and intelligence, even going so far as to bend police rules to assist him. Ichijo is not merely a support character; he also actively participates in combat. Using special bullets and rifles developed by the Science Police, he engages the Gurongi directly, demonstrating remarkable marksmanship and personal bravery, often putting his own life at risk.

One of the most significant key relationships is with Yusuke Godai. What begins as a reluctant alliance born of necessity deepens into a strong friendship built on mutual respect and trust. Ichijo becomes the primary figure who understands and supports Yusuke’s burden. Another important relationship is with his mother, to whom he speaks in the Nagoya dialect, revealing a softer, more personal side to his otherwise stoic character. He also has a connection to the Gurongi, particularly the female leader La Baruba, being the only human in the series to confront her directly.

Throughout the series, Ichijo undergoes notable development. He transitions from a by-the-book officer who is skeptical of a civilian fighting force to a man who willingly breaks protocol to ensure Yusuke can succeed. His character arc is defined by this partnership and his growing personal investment in Yusuke's wellbeing, culminating in the final battle. Before the ultimate confrontation, Ichijo is tasked with a terrible responsibility: to shoot Yusuke’s Arkl, the very source of his power, if things go wrong, effectively asking him to be prepared to kill his own friend to stop the enemy. This moment represents the extreme difficulty of the sacrifices required of him. After the final battle and the defeat of the Gurongi, Ichijo returns to the Nagano Prefectural Police, his duty fulfilled.

As for notable abilities, Ichijo is a highly skilled and courageous police officer. His marksmanship is exceptional; he can accurately fire a gun to disarm an enemy holding a hostage. He is proficient in using advanced police weaponry, including large-caliber revolvers and specialized rifles designed to combat the Gurongi. Despite his human body, which is frequently injured in battle, he shows a remarkable resilience, consistently returning to the front lines even after sustaining serious wounds. Beyond his combat skills, his true strengths are his sharp intelligence, his insightful nature, and his unshakeable dedication, which prove to be as vital to the fight as Kuuga’s physical power.