I fully believe that Gosho never originally intended for Kaito and Shinichi to be related, and that he only planned to feature KID in Detective Conan as a homage to his older work, Magic Kaito. But as time went on, demand for a Magic Kaito continuation started to rise, so Gosho probably tried to kill two birds with one stone by making KID a recurring character.
At some point during development, KID became more and more integrated into the main plot. Originally, he was just fanservice — a part of the series that wasn’t supposed to affect the story much. But ever since Kaito helped Conan save Haibara, the rest of his heists have involved him interacting more and more with the Detective Conan cast and learning more about them. Even the Gathering of Detectives case was later retconned into a major part of the series.
This turns Magic Kaito into a Detective Conan’s spin-off. I'll elaborate about this further on how this could be a good thing in the conclusion.
The next post will be about the development of Kaitou KID in Detective Conan.














