Old Octopus, known in the film's original Japanese materials as Tako-baba, is an elderly resident of the seaside town of Hinashi Town in the anime film Lu Over the Wall. Her name belongs to the film's pattern of naming characters after seafood, and she is part of the older generation that preserves the town's customs and its deep-rooted caution about the sea.

Her background is marked by a personal tragedy. Long ago, someone she loved was pulled into the sea by a mermaid and never returned, an event she has never forgotten and believes she cannot forgive. This loss is the foundation of her personality: she is wary, stubborn, and openly resentful toward merfolk, whom she regards as dangerous and untrustworthy. Her fear is not abstract, as it is for many of the town's residents, but rooted in grief, which makes her one of the most vocal believers in the local legend that mermaids are man-eaters.

Her central motivation is vigilance. She wants to protect her community from what she sees as a real threat, and she spends her days watching the sea from an elevated position, keeping lookout for any mermaid that might approach the town. She is depicted as an ordinary human elder with no supernatural abilities; her watchfulness and her forceful opinions are her defining traits.

In the story, Old Octopus stands as one of the town's strongest opponents of the merfolk, and her suspicions put her in conflict with the younger characters, especially the mermaid Lu, who arrives hoping to befriend humans. Her relationship to the community is shaped by her loss, as she serves as a living reminder of why the town fears the sea, while her personal history also makes her one of the most sympathetic voices on the side of tradition, since her hostility grows out of genuine pain. The film does not show her changing her views; instead, she consistently represents the old distrust that the younger generation must overcome before the town can accept the merfolk.