Ojarumaru is a five-year-old noble prince from the Heian-era Fairy World, born into the aristocratic Sakanoue family. His features include light skin, black eyebrows, and brown hair, complemented by traditional sokutai robes, a dark blue eboshi headpiece, and green shoes. He dons light yellow pajamas for sleep and habitually tucks rare treasures inside his eboshi.

His personality blends a relaxed, leisurely nature with a penchant for avoiding strenuous tasks, favoring quiet days over exertion. Though whimsically curious, he displays a spoiled, self-centered edge. He harbors a strong dislike for water and often relies on companions like Kazuma, who carries him during excursions. His speech reflects aristocratic roots, marked by archaic polite Japanese phrases, distinctive exclamations like “Oja” or “Ojahoho,” and sentence endings such as “de ojaru.” Mispronounced words, frequently corrected by peers, pepper his dialogue.

After stealing the Great King Enma’s judgment scepter, he flees to modern-day Japan, pursued by the Kooni Trio—three oni siblings tasked with reclaiming the artifact. Settling in Moonlight Town, he bonds with Kazuma Tamura’s family and his caretaker Denbo, a firefly-like spirit. Relationships range from teasing rivalries with the Kooni Trio, whom he mocks with derogatory nicknames, to a brotherly rapport with Kazuma, occasionally strained by minor disagreements.

A 17-year-old version of Ojarumaru appears in the 25th-anniversary special *Heianchō Onigami Kessen*, though developmental specifics remain undocumented. Throughout all iterations, he retains his aversion to effort, fascination with oddities, and knack for navigating playful clashes with foes while adjusting to contemporary life.