Police Sergeant recurs as a law enforcement counterpart to the protagonist. His duties necessitate repeated encounters with the hitman, forging a persistent adversarial dynamic that evolves beyond simple professional opposition, gaining personal nuances.

Their interactions include an accidental store meeting where their hands touch reaching for the same item, framed within a legal metaphor yet suggesting deeper complexity. Further exploration occurs through late-night phone calls initiated by the hitman. These escalate into competitive comparisons of opposing concepts—day/night, water/oil, light/shadow—lasting until morning and revealing a peculiar mutual engagement transcending their official conflict.

Their confrontations sometimes take unconventional forms. At a children's amusement park, both disguised as animal mascots alongside the hitman's target, the Sergeant attempts an arrest. This triggers a three-way skirmish misinterpreted by children as entertainment.

A significant development arises when the Sergeant travels to Lake Yashiroko seeking a fresh start. Realizing that "Yashiroko" spelled backward reads as "Koroshiya" (hitman), he exhibits visible distress, indicating an inability to mentally escape their fraught connection despite physical separation.