Hoyuelo is a recurring spirit who first appears as an antagonist but eventually becomes a constant companion to the protagonist. His name, which translates to "small dimple" or "little hollow," reflects his eventual diminutive form and playful nature.

In his initial appearance, Hoyuelo presents himself as a powerful and charismatic spirit who had been acting as a messiah for a cult called the "Ha Ha Ha" group, dedicated to laughter and joy. He becomes intrigued and irritated by Shigeo Kageyama, Mob, because Mob rarely smiles or laughs. To provoke a reaction, Hoyuelo challenges Mob to a staring contest, which Mob wins due to his inability to laugh as his emotional suppression begins to build. The confrontation escalates into a fight, and Mob defeats him. However, rather than exorcising him completely, Mob inadvertently reduces Hoyuelo to a small, weak specter resembling a wisp of green smoke with rosy cheeks, who then begins following Mob everywhere.

Personality-wise, Hoyuelo is cunning, ambitious, and street-smart, often acting as a rude, cynical foil to Mob's earnest and naive sincerity. Despite his self-serving nature, he takes on the role of a wise, unsolicited advisor, offering blunt, practical advice that contrasts sharply with Mob's gentle worldview. He openly admits to his own selfish desires, such as his initial goal to possess Mob's powerful body and his later schemes to gain followers and power for himself. He is prone to grandiose speeches and elaborate plans, yet his interactions with Mob gradually reveal a more complex, caring side beneath his boastful exterior.

Motivation for Hoyuelo evolves significantly throughout the story. Initially driven by a desire for power, followers, and a physical form, his goals shift as he spends more time around Mob. While he continues to crave recognition and influence, his primary motivation becomes intertwined with Mob's well-being. In the third season, his elaborate scheme involving a giant Divine Tree and the creation of a cult-like following is revealed to be, at its core, a cry for attention from Mob himself. He craves Mob's acknowledgment and friendship more than the adoration of the masses.

In the story, Hoyuelo serves several vital roles. He is a companion who remains with Mob constantly, floating near his shoulder. He often acts as a commentator, a source of exposition about the spirit world, and a voice of selfish reason that challenges Mob's selfless decisions. His presence allows for moments of dark humor and provides Mob with a perspective he would otherwise lack.

Key relationships define his character arc. His most significant relationship is with Mob. What begins as a master-defeated-servant dynamic slowly transforms into a genuine, if unspoken, friendship. Hoyuelo sees Mob as a naive but powerful master and, eventually, as a friend who needs someone to tell him the truth. Mob, in turn, trusts Hoyuelo implicitly, at one point even lowering his psychic defenses completely because he trusts his spirit companion. Their bond is one of mutual respect and dependence, with Mob serving as an anchor for Hoyuelo's morality and Hoyuelo serving as a protector and advisor for Mob.

Hoyuelo also has a distinct but less developed relationship with Reigen Arataka, Mob's human mentor. The two often bicker, squabble over influence on Mob, and serve as competing guides in Mob's life, representing cynical pragmatism versus charming deception.

Hoyuelo experiences considerable development. He transitions from a self-proclaimed evil spirit and a would-be world conqueror to a loyal friend who is willing to sacrifice his own ambitions for Mob's safety. His third season arc forces him to confront his own feelings, acknowledging that the only person whose validation he truly seeks is Mob's. This emotional honesty represents a profound change from the scheming spirit introduced at the beginning of the series.

As for notable abilities, in his diminished state following his defeat, Hoyuelo has very limited power. He can fly, become intangible, levitate small objects, and speak telepathically or audibly. He cannot physically interact with the world in a significant way and is easily dispersed by stronger psychics or spirits. However, if he manages to possess a living human or a sufficiently powerful vessel, he can access and utilize all of that person's psychic abilities in addition to his own cunning and experience. His true strength lies not in raw power but in his intelligence, charisma, psychological manipulation, and his deep, accumulated knowledge of how the spirit world operates.