Kenji Satō is a young boy with short brown hair who usually wears a baseball cap. Initially skeptical, he dismissed supernatural investigations as fraudulent and vandalized a magical law consultancy's sign. His disbelief held until an incident in a bamboo forest: during a dare, he removed a seal, accidentally freeing a blood-drinking ghost that threatened him and his friends. This forced him to confront the reality of spirits.

Rescued by the magical law enforcers, he developed strong admiration for them. He affectionately nicknamed one "Onion-Boy" and the other "Bean Sprout." Despite a strict policy against post-case client meetings unless new issues arose, he frequently sought excuses to visit their office, showing persistent attachment and curiosity about their work.

He loves pranks, sports, and hamburgers, while disliking studying, vegetables like carrots and onions, and routine activities such as playing the recorder. Naturally athletic, he excels in various physical activities but also displays talent for evading responsibilities and causing mischief.

His established role remains that of a recurring, supportive figure with unwavering loyalty to the protagonists.