Another Son of Satan (Blue Exorcist x Detective Conan x Magic Kaito Fanfic)

In Beika City, a well-known young detective named Kudo Shinichi has returned to his old life after defeated his enemy, The Black Organization...Everything went normally until he delivered an odd and old key in a black envelope...At first, he thought that it might be Kaito who gives the key...Not until when a mysterious voice echoed in his mind and told him that he was son of Satan! Who is the owner of the mysterious voice? What will happen to him? How could he be Satan's son? What does the voice want with him? Read to find out...