Keiichi Ikari is a middle-aged detective serving as the chief investigator assigned to the Shonen Bat case. A slightly overweight man with black hair, a receding hairline, and a short mustache and goatee, he typically dresses in an open buttoned coat, dress pants, and a red belt. His appearance reflects his nature as an old-fashioned, grounded individual who feels increasingly out of place in a changing world. He originally joined the police force with a nostalgic, almost romanticized desire to chase the classic image of thieves in bandanas carrying burlap sacks, but he has remained in law enforcement for the long term, now grappling with modern criminals and a society he finds unfamiliar.

Ikari's personality is defined by his quick temper, skepticism, and a deep-seated resistance to delusion. Years of dealing with disrespectful youth and sophisticated criminals have made him blunt and prone to losing his patience, particularly with his more optimistic and open-minded partner, Mitsuhiro Maniwa, whose views frequently clash with his own. Ikari is naturally skeptical, always seeking the most logical explanation for events, and he initially believes the Shonen Bat attacks are likely a hoax rather than the work of a supernatural or mysterious assailant. Beneath this gruff exterior, however, he is a man burdened by personal responsibility, as he is married to Misae Ikari, a woman suffering from a debilitating heart condition. The stress of the investigation reignites a smoking habit he had previously quit, and he even reverts to an old brand of matches, a small but telling detail that underscores his feeling of being stuck in the past.

Ikari's primary motivation is his duty as a detective, but this is inextricably linked to his role as a provider and pillar of support for his ill wife. He works hard to pay for her medical expenses and to remain strong for her. His role in the story serves as a counterbalance to the growing mass hysteria surrounding Shonen Bat. While the public and even his partner become captivated by the legend and the psychological escape offered by the mascot character Maromi, Ikari remains a stubbornly rational figure. His relationship with Maniwa is central to the investigation; where Maniwa tries to read between the lines and explore abstract theories, Ikari insists on straightforward, evidence-based conclusions. This dynamic creates a persistent tension that drives much of the detective work in the series.

The character undergoes a significant internal development as the series progresses and the influence of Shonen Bat's darkness spreads. Ikari finds himself drawn into a personal fantasy land, an idealized world of his own making where he plays the hero and where Tsukiko Sagi is imagined to be his daughter. This escape represents his deep yearning for a simpler, more just time where he could be an unambiguous force for good. His return to reality is catalyzed by the death of his wife, Misae. She is one of the few characters who successfully resists Shonen Bat, not through force, but through an unshakable strength of spirit. Her final act of love and her determination to rescue her husband from his sadness give Ikari the necessary resolve to shatter his own fantasy and confront the real crisis. This act of breaking free from delusion makes him instrumental in helping Tsukiko Sagi do the same.

Keiichi Ikari’s most notable ability is not a physical skill but his exceptional mental resilience. He possesses a powerful resistance to the mass delusion and escapist fantasies that consume most of the other characters. While he is briefly tempted by his own ideal world, his fundamental convictions and the memory of his wife’s strength allow him to tear down that illusion and face the harshness of reality. This capacity to reject comforting lies and accept the truth makes him one of the few genuine heroes in the narrative, providing a necessary anchor to reality when the city is overwhelmed by paranoia and逃避.