Bonobono's father is a mature sea otter who resides with his son near a forest by the ocean. He is an older, larger version of his son, bearing a strong physical resemblance to him. His most defining characteristic is his incredibly slow and gentle demeanor. He speaks very deliberately, often with noticeable pauses between his words, and his actions are consistently relaxed and unhurried, presenting an outward appearance that is often described as simple or foolish. He enjoys solitary, imaginative play and possesses a great deal of patience, listing his special skill as the ability to endure. A doting and dedicated parent, he has raised Bonobono on his own and shares a close, affectionate bond with him, frequently inventing creative and unique games to play together.

Despite his unassuming nature, Bonobono's father harbors a surprising and legendary past. In his youth, he was known among killer whales as the sea otter, the god of death, a being so formidable that even the natural predators of sea otters fear him. This reputation stems from an incident where he was swallowed whole by a notorious, villainous killer whale. Remaining completely calm and unperturbed while inside the creature, he ultimately caused its death, solidifying his status as a hero and an object of fear among the killer whale community. He maintains a friendship with a killer whale named Scar, who knows the truth of this story, and occasionally visits his territory using a peculiar swimming method to avoid being pursued by other killer whales. This hidden strength is also evident in his physical power; he once won a duel against the Brown Bear Captain, the formidable leader of the forest, over the rights to a sandy beach.

The role of Bonobono's father in the story is primarily that of a kind and eccentric parent who supports his son's gentle curiosity about the world. His past as a legendary figure provides a stark and often humorous contrast to his present-day laid-back personality, serving as a source of wonder and unexpected wisdom. His motivations are deeply rooted in family and the act of living with sorrow. The story reveals that his wife, Raco, died shortly after Bonobono's birth. She had fallen into a deep depression following the death of a close friend, and though Bonobono's father tried to comfort her, she eventually passed away, leaving him alone with their newborn son. Overwhelmed by grief, he too began to waste away in sadness. However, following the advice of a friend, he resolved to live fully for the sake of his son, choosing to carry his sadness with him and trusting that, in time, living would make things better. This backstory shapes his core motivation: to be a present and loving father for Bonobono, having decided to live with his pain rather than succumb to it.

Bonobono's father has several key relationships beyond his son. He is an acquaintance of the Whale Elder, an old killer whale who understands his past and serves as a mentor figure to Bonobono when the young otter glimpses his father's mysterious other side. He is also on friendly terms with sharks, demonstrating a wide and unexpected circle of acquaintances. His development is not about a change in personality, but a revelation of depth. The initially simple and goofy father is gradually shown to be a figure of immense, quiet strength and profound resilience, having endured a tragic past and earned a legendary reputation, all while maintaining a gentle spirit for the sake of his son. His notable abilities, rarely displayed, include his legendary status as an undefeatable fighter among killer whales, his surprising physical strength in confrontations like the duel with the brown bear, and his immense capacity for patience and emotional endurance.