Kenji Sato is a young boy with short brown hair who always wears a baseball hat. He initially earns a reputation as a troublemaker, openly dismissing ghosts and actively disrupting Muhyo and Roji's operations by destroying their business sign. Fueled by skepticism, he participates in a test of courage at a supposedly haunted temple to disprove supernatural claims. During this event, he unwittingly releases a blood-drinking ghost, placing himself in grave danger. Muhyo and Roji intervene to save him, forcing Kenji's first direct encounter with the supernatural and fundamentally altering his disbelief. Following this rescue, Kenji develops a strong affinity for Muhyo and Roji. He frequently visits their office seeking opportunities to observe or assist with cases, despite Muhyo’s rule against meeting clients post-case unless they bring new business. Kenji affectionately assigns the duo nicknames, calling Roji "Sprout-Man" and Muhyo "Onion-Boy," reflecting his playful demeanor. His persistence is clear when he independently infiltrates their office, underscoring his determination to stay involved in their supernatural investigations. Kenji exhibits a spirited and impulsive personality. His talents lie in sports, pranks, and evasive maneuvers. He openly dislikes academic activities, desk-bound tasks, playing the recorder, and vegetables like carrots and onions. His preferred foods include hamburgers, and he displays a fondness for round objects, often engaging in playful throwing. While his role remains supportive, his loyalty to Muhyo and Roji is evident through his recurring presence and eagerness to contribute to their efforts.