"I have also been thinking about another issue: what if there is a Magus who thinks like me but cannot clarify the key point, or finds it too difficult to outwardly project their 'world,' and thus only advances their magic by learning each magic template one by one?"
"With time, these people will accumulate enough to become extremely powerful high-class Magus, but they will never be able to become grand-class Magus. Because even if they learn everything and bend every single magic system, it can never equal the comprehensiveness of this world, can it?"
It was not wrong that grand-class Magus could nullify any magic system, but it was not because they could do so that they were grand-class Magus.
They were already a "world"—a world with a consciousness—so the so-called nullification of all magic systems was merely a side effect, not the main point.
