Based on two manga series by Kimio Yanagisawa: "Tokumei Kakarichou Tadano Hitoshi" (9 volumes) & "Shin Tokumei Kakaricho Tadano Hitoshi" (11 volumes).
In the original manga Hitoshi Tadano (Katsunori Takahashi) works solo, but in the TV series works with a sidekick named Koichi Muriwaki (Masaru Nagai).
After the TV series aired, Tadano's sidekick Muriwaki was written into the manga.