Daisuke Fujiwara first appears as a young boy in a rural village. Rescued from rogue dogs by Riki as a child, this event forged his deep, lifelong connection with canines. His affection is clear when he excitedly explains the meaning behind his Akita puppy Gin's silver fur at birth. In childhood, Daisuke displays a headstrong, impulsive nature, often acting without permission and occasionally bullying girls. Yet, he shows greater problem-solving initiative than other villagers and intelligence when calm. He clashes initially with the elderly bearhound trainer Gohei Takeda over Gin's harsh training, but develops respect as the methods prove effective against the bear Akakabuto. Similarly, his early dislike for the hunter Hidetoshi evolves into respect through shared experiences. Daisuke possesses strong determination, training rigorously with bow hunting to confront Akakabuto despite initial fears about killing animals. When Gohei becomes bedridden, Daisuke assists in Gin's training. He eventually masters the bow, successfully hunting a large female bear alongside Gin. Though devastated when Gin leaves to join the wild Ohu dog pack, Daisuke maintains faith Gin will return for Akakabuto. After the final battle, he understands Gin belongs with the wild pack despite his reunion joy. Later, he witnesses Gin's farewell to the dying Gohei.

As an adult in later series, Daisuke matures into a calmer, kinder, more polite individual, retaining his profound love for dogs. He maintains a long-distance relationship with his girlfriend Kazu. Hearing reports of a mountain monster, he investigates his old hunting grounds with Gin and encounters the injured puppy Weed, immediately recognizing him as Gin's son due to their resemblance. After Weed saves him from the monster Kaibutsu, Daisuke nurses Weed's gunshot wounds. Later, he returns with Hidetoshi and his bow to aid the dogs against Kaibutsu, shooting the fatal arrow into its chest. He continues monitoring wild dog activities, learning about the threats from Hougen and Genba via Shouji Sudou. He refuses to participate in the villagers' plan to bomb Gajou, finding it abhorrent. Following Hougen's defeat, he finds and heals the wounded Jerome. When pet dogs vanish en masse to follow Weed to Hokkaido, Daisuke and Hidetoshi track them, arriving in time to witness Gin near death after a battle. Daisuke's desperate shout helps revive Gin, and he stays to aid injured dogs from both sides. After the bear threat ends, he briefly reunites with Gin at home, bathing him and spending the night together before accepting Gin's return to the wild. He later visits Gin regularly with Kazu, bringing treats and eventually naming Gin's grandchildren while stargazing.

In subsequent storylines, Daisuke continues his supportive role. He and Hidetoshi feed Gin's grandchildren (Orion, Rigel, Sirius, Bellatrix) until their mother Koyuki calls them back. The ninja dog Akame later saves them from a landslide during their descent. After a major earthquake and volcanic eruptions, he worries about the puppies but takes the appearance of the Orion constellation as a positive sign. Hidetoshi introduces him to his new dog Andy, John's nephew. Later, encountering Rigel and Kotetsu, he recognizes Rigel and cares for them before following them to discover Gin and the Ohu pack locked in a shed. He locates Kurohabaki Jinemon, secures the key, and frees the dogs. After Kurohabaki Masamune's defeat, he escorts Jinemon to meet the volcano-surviving dogs, receiving a greeting bite from Orion before departing. During a helicopter flight with Hidetoshi in later conflicts, their arrival scares off Monsoon's bears, allowing them to evacuate the wounded Weed and George for veterinary treatment. Later, alerted by a boy who found an injured Gin near a stream, Daisuke initially believes Gin dead but discovers a faint heartbeat and rushes him to the vet. He later arranges food for Gin's companions Cross, Sunny, and Maru despite his parents' reservations.