However, even if someone else would withdraw the mana from the magic gem in order to use it for magic, I guess they would be able to draw out at most 5% of the stored mana.
Even though there are many magic tools that don’t have this limitation, the magic tool artisans are every time forced to ask magicians with the same very rare ability of sharing mana nature like Burkhart-san to engrave the formula into their tool.
In addition, because Burkhart-san didn’t possess the ability to produce magic tools, the result was that he could only use that mana transfer if the other party was a human.