BP-119 Duke, also known as the Knight Detective, he can combine with the Fire Roader to form Duke Fire, then combine with J-Decker (BP-110 Deckerd + J-Roader) to form Fire J-Decker.

The number 119 in Duke's serial code is the emergency number for Japan's firefighting and ambulance services, reflecting Duke's vehicle mode as an ambulance and the Fire Roader.

Duke's alternate mode is an ambulance. He possesses a very grounded personality with strong senses of duty, honor, and loyalty, which can make him inflexible and stubborn at times. Spending his formative times under Regina's tutelage, she pushed him towards an unrealistic idea of perfection due to past traumas and the obsession of making a "perfect policeman." While Duke did manage to overcome most of this early conditioning, it still does occasionally show with his struggles of dealing with emotions and somewhat stiff personality. He has a strong loyalty and connection to his creator, Regina Argine, whose demeanor towards him has softened in recent times with her conquering some of the demons of her past. A newcomer to the team, he also does not always fit in with the others in the Japanese Brave Police and this can cause conflicts. Duke is passionate about nature, and in particular likes sea life like whales.

Technology-wise, Duke was developed from the leadership traits of BP-301 McCrane, BP-302 Power Joe's agility, BP-303 Dumpson's power control and BP-501 Shadow-Maru's reconaissance abilities. Similar to the rest of the Brave Police, he is armed with a standard-issue revolver and a Brave Police mechanical notebook, with his signature weapon being a broadsword.

Due to the circumstances of his creation, Duke always refers to Regina as "Lady", and rarely refers to her by her given name.