Sueo Maruo is a recurring classmate in Chibi Maruko-chan, known for being studious, serious, and overly formal. He often acts like a model student and tries to present himself as refined and responsible, which makes him a source of comedy when his self-image clashes with the more casual behavior of the other children. He serves as a familiar supporting character in Maruko’s classroom, often representing the type of boy who takes school and social rules very seriously.