Kenji Sato (佐藤 健二, Satō Kenji) is a trouble-making boy who had believed Muhyo and Roji's business was a fake and destroyed their sign. He did not believe in ghosts until the pair saved him from a blood-drinking ghost he had accidentally freed.
Kenji is a young boy with short brown hair and usually always wear a baseball hat.
He loves to make pranks and wasn't believing in ghosts until it was saved by Muhyo and Roji. Afterwards, Kenji grew a liking for the pair, often referring to Roji as "Sprout-Man" and Muhyo as "Onion-Boy". He always tries to find excuses to hang around their office, as Muhyo has made it a rule never to meet a client after the case is complete unless they bring a new one.
- He likes hamburgers, balls (will throw anything round), Jabin (a devoted reader for two years)
- He dislikes studying, sitting at a desk, playing the recorder, carrots, all kinds of onions
- He is talented in all sports, running away and playing pranks.