Koichi is the father of Sosuke and the husband of Lisa in the anime film Ponyo on the Cliff by the Sea. He works as the captain of a fishing boat called the Koganei Maru, a job that keeps him at sea for extended periods. His family lives in a house perched on a cliff overlooking the ocean, and Koichi frequently communicates with them by using signal lamps from his ship as he passes by. He is a dedicated and hardworking sailor who deeply cares for his wife and son, although his long absences sometimes create tension in his relationship with Lisa. Koichi maintains a close bond with his son through their shared interest in ships and Morse code, and he is shown to be a loving father despite the physical distance. During the great magical storm that sweeps through the coastal town, Koichi finds himself at the center of the supernatural events at sea. He witnesses extraordinary phenomena, including the appearance of the sea goddess Granmamare, whom he and his crew respectfully acknowledge as the Goddess of Mercy. His role in the story is largely external; he survives the perilous storm and the ship graveyard caused by Ponyo's magic, and he is eventually reunited with his family after the waters recede. Koichi’s experiences at sea highlight his resilience and his ability to navigate both ordinary and extraordinary circumstances. He is a practical and compassionate figure who supports his family from afar and respects the natural world, treating its mysteries with humility. His development is subtle, centered on enduring the chaos and returning to his loved ones, reaffirming his commitment to them. Koichi’s notable abilities include his seamanship, skill with navigation and signaling, and his knowledge of Morse code, which he uses to stay in touch with Sosuke and Lisa.