The storyline of 20 Mensou ni Onegai!! occurs simultaneously with both CLAMP Gakuen Tanteidan and Gakuen Tokukei Duklyon. As demonstrated by a conversation between Nokoru and Suou which also takes place in CLAMP Gakuen Tanteidan, while in Duklyon Akira and Utako appear at their age as they do in 20 Mensou ni Onegai!!.
The manga took inspiration from the works of Edogawa Rampo, most notably from Kaijin Nijuu Mensou (The Fiend with Twenty Faces).
The manga has been published in English by TokyoPop on May 6, 2003 and Jul 15, 2003 respectively.