Kōshirō Daimon, a 36-year-old police officer, serves alongside his older twin brother, Kenshiro Daimon. Their shared history is shaped by the traumatic loss of their parents in a hit-and-run taxi accident during their youth, fueling a deep-seated mistrust of taxi drivers and the protagonist, Hiroshi Odokawa. Kenshiro’s cynical, manipulative nature starkly contrasts Kōshirō’s naive demeanor, talkative tendencies, and unyielding moral compass—traits that bind the brothers despite clashing approaches to law enforcement.

Kōshirō’s career is plagued by moments of absentmindedness and a habit of unintentionally leaking confidential details, fostering perceptions of incompetence among colleagues like Odokawa. Driven by a straightforward resolve to punish wrongdoers, his idealism is tempered through his brother’s pragmatic worldview. This dynamic fractures when Kōshirō receives damning evidence from Odokawa that implicates Kenshiro in collusion with gangster Dobu, forcing him to confront fractures in his loyalty.

After a shooting involving Dobu, Kōshirō dodges firearm inspections to avoid scrutiny, exposing his struggle between duty and self-preservation. This conflict peaks when he uncovers Kenshiro’s corruption, culminating in his reluctant decision to arrest his brother—a defining act cementing his allegiance to justice above blood ties.

The film *Odd Taxi: In the Woods* recontextualizes series events without expanding Kōshirō’s personal arc, instead reaffirming his role in the collective resolution. His journey remains anchored in shedding naivety to prioritize ethical integrity, even as he confronts his brother’s moral collapse.