Kôichi, Sosuke's father and Lisa's husband, works as a sailor aboard the Koganei-maru. His job keeps him away from home for long stretches, leading to frequent absences from his family's cliffside life. This distance fuels recurring tension, especially with Lisa, who voices frustration when work delays his promised returns. Despite being away, Kôichi connects with his family using maritime communication methods. He sends messages via Morse code signal lamp to Lisa and Sosuke, striving to bridge the gap. Once, after missing a homecoming, he activated the ship's decorative lights as an apology, a gesture that mesmerized Sosuke. Kôichi reveals a practical nature; witnessing Ponyo running atop magical storm waves, his sole observation noted her approximate age, not the impossibility. During a severe magically-induced storm, Kôichi observed the approach of Ponyo's mother, Granmamare, recognizing her as the Goddess of Mercy. His ship's stalled engine restarted amid this encounter, an event the crew credited to divine protection. His role remains defined by his duties as a sailor and his commitment to providing for his family, despite the required sacrifices.