Harry Goodman is the father of Tim Goodman and a central figure in the story, though he is physically absent for the majority of it. He was an accomplished and highly respected detective working in Ryme City, known for his professional dedication and his willingness to face danger to solve cases and help both people and Pokémon in need. He was a regular patron of the Hi-Hat Café and had a deep love for coffee.

Goodman had a partner, a Pikachu who assisted him in his investigations. The two shared a strong bond and formidable skills, having once battled together to defeat a Charizard in an underground arena. This incident left visible scars on the Charizard, indicating Goodman and his partner were a force to be reckoned with.

Prior to the events of the story, Goodman's wife passed away, which had a profound impact on the family. After her death, Goodman moved to Ryme City and immersed himself in his detective work, leaving his son Tim to live with his maternal grandmother. This led to a strained relationship between father and son. While Goodman did extend an offer for Tim to join him in the city, Tim refused, feeling abandoned by a father who seemed to care more about his career than his family. Despite the distance, it is later revealed that Goodman had prepared a room for Tim in his apartment and kept it clean for years, holding onto the hope that his son would one day choose to live with him.

Goodman's role in the story is as a catalyst. He was hired by Howard Clifford, the founder of Ryme City, to help capture the legendary Pokémon Mewtwo. However, upon discovering that Clifford planned to use Mewtwo for a malevolent purpose involving a substance known as R gas, Goodman and his Pikachu had a change of heart. They betrayed their employer, sabotaged the laboratory, and helped Mewtwo escape. In retaliation, Clifford sent his Greninja to eliminate them, resulting in a car crash that left Goodman severely injured.

In a desperate attempt to save his life, Mewtwo used its psychic powers to merge Goodman's soul with his Pikachu's body, erasing the resulting entity's memories in the process. This new being, which retained the speaking voice and some personality of Harry Goodman, became the talking Detective Pikachu who would later seek out Tim. This symbiotic state endures for most of the narrative, with the Pikachu character acting on the detective instincts and underlying love for his son that remained within him.

The key relationship in Goodman's story is with his son, Tim. The entire narrative is driven by Tim's journey to uncover the truth about his father's disappearance, a process that forces him to confront his feelings of abandonment and ultimately reconcile with Harry's memory. The climax of the story sees Mewtwo separate Harry and Pikachu, restoring Goodman to his original human form. In this moment, he is finally able to have a true reunion with his son, resolving the emotional conflict that defined their past.