Enma Daiō rules as King and Head Judge of the Japanese underworld, determining each soul's destination in hell based on their sins. His immense stature features red skin, black hair, and traditional robes echoing Tang Dynasty officials, often topped with a horned crown or helmet. He maintains underworld order aided by his chief deputy, Hozuki. Though stern and judicial while working, Enma displays a surprisingly gentle, goofball personality off-duty. He frequently suffers physical ailments like slipped discs, requiring Hozuki's intervention. His love for sweets, especially Baumkuchen, is well-known, as is his enjoyment of sharing mundane stories about his grandchildren.

Enma's relationship with Hozuki is central. Despite holding higher rank, Enma heavily depends on Hozuki to manage hell's daily operations, political affairs, and his personal health, effectively making Enma an Alleged Boss. Enma expresses fondness for Hozuki, addressing him casually as a friend or father figure, yet endures frequent verbal abuse and sadistic punishments from his deputy. Their history stretches back to ancient times when Enma named the orphaned human-turned-demon "Hozuki" and appointed him chief of staff. Enma places absolute trust in Hozuki despite this overt disrespect.

In governing the underworld, Enma collaborates with the Ten Kings of Hell during official meetings and defers to the seniority of Izanami-no-Mikoto, the original Chief of Staff. His background involves establishing the Japanese hell system, with Hozuki designing its structure during their first encounter. Enma's judgment style balances strict protocol with occasional leniency, reflecting his mythological role as a compassionate figure beneath his fearsome exterior. This aligns with his Buddhist origins as an incarnation of Jizō Bosatsu, the guardian seeking to save souls from suffering.

Later developments show Enma adapting to hell's evolving challenges, including staffing changes and Hozuki-driven administrative reforms. His interactions expand to include new characters like the twin zashiki-warashi spirits adopted by Hozuki, though Enma remains largely reactive to these additions. His core traits—reliance on Hozuki, off-duty kindness, and comedic suffering—persist consistently across all media depictions, including anime seasons and OVAs.