Old Man Carl, Kāru Ojisan in the original Japanese, is a character in the anime Mechanical Marie. He is a distant relative of Arthur, the heir of a major financial conglomerate around whom the story’s household revolves. Carl’s most defining trait is his kindness toward Arthur. Within Arthur’s family, he stands out because most of the relatives dislike Arthur and reject him, while Carl is the only one who treats him with genuine warmth and consideration.

This places Carl in a unique position among the people in Arthur’s life: he is the sole family member who offers Arthur caring, positive treatment rather than hostility or coldness. In the story, Carl functions as a gentle presence in Arthur’s world, and his friendly manner toward Arthur sets him apart from the rest of the family. His relationship with Arthur is built on this kindness, and he represents the rare example of familial goodwill within a family circle that otherwise tends to view Arthur negatively. His amiable and considerate treatment of Arthur is what defines his place in the narrative.