As we all know, in Kaitos version, magic is real (Akako). Magic is also a thing in this. Pandora contains magic, magic only a true wizard could control.

In this, most people are able to use magic. Kaito is aware of having magic, but he hasn't released his true powers, same for Shinichi (not that they know that).

The legend about the gem goes through all sorts of theories, like granting immortality or even turning the one into a demon. Many people believe you have to work hard and practice magic till its perfect. Others believe its just a story to make people use their powers and find a gem that will just waste their time.

The thing is, Kaito and Shinichi don't care about having such great power, also because they thought it was a well-made story to give the wizards and witches something to do.

What they all don't know is, the gem won't light up until the one has died. The gem finds its way to the wizard or witch and replaces their heart, so they can live again with their power. Also maybe that they could find the one that will hold them close in bad times and good, and will always put them first. (The Gem will also light up as the colour of that person's eye colour.)