O-jiro, a ghost and the youngest brother of Q-taro, belongs to a family of supernatural beings. His small, round yellow body sports black eyes and a single strand of hair protruding from his head. Despite his infantile form, he displays advanced manual dexterity and repair skills, crafting functional items such as socks from newspaper. Communication occurs through nonsensical phrases—"Bakeratta," "Naniratta?," "Baccaratta!," "Dummelerta," and "Aholachta"—which only Q-taro fully understands, requiring the older brother to translate for others. O-jiro’s explosive ability activates when he shouts "Bom!" or "Pa!," detonating objects or clearing obstacles nearby.

His family includes X-zō, a shadow-like ghost father, and O-zetto, his round-bodied mother adorned with a floral hair accessory. Alongside older brother Q-taro and younger sister P-ko, they reside with the human Ohara household, where O-jiro partakes in daily antics. His personality blends childlike mischief and curiosity, mirroring a kindergarten-aged child’s playful tendencies. Though limited in speech, he demonstrates intelligence through inventive problem-solving and creative application of his explosive powers. Interactions with humans like Shota and Shinichi Ohara reveal his integration into their world, albeit with frequent misunderstandings due to his unique communication style.

O-jiro’s role remains consistently comedic and static across portrayals, centered on familial bonds and lighthearted chaos without significant narrative evolution.