This was the limit of a Saint who mainly used close-ranged combat.

Maybe Acqua had some body defense spell that was even more refined than this.
Though Kanzaki thought of a few possibilities herself, no matter what, she
failed.

As expected, there would be a problem if she powered up to his level. If she used
a similar power to that of Acqua’s. If anyone tried to use the power that Acqua
used, at that moment, an ordinary person’s body would have eroded, whether
physically or magically.

(Acqua’s…power is…)

Normally, the power given to a Saint couldn’t be used entirely.

Since they were people who had similar body characteristics with the Son of
God, Saints were those who were said to have inherited his power; even if it was
just a part of it, in the end, it was not something that a human could grasp.

They had a part of that power, but trying to grasp a part of that part of power was
already tough for a Saint.

This was the real identity of a Saint.

No matter how they built this up, there would be a divide that they couldn’t
surpass. If one had to describe it, it would be like finally getting hold of a power
only for it to scatter like fog. Thus, there was a limit to using the power created
through the Idol Theory with their own willpower.

However, this wasn’t completely bad. If Saints could use such power at 100%,
the high pressure would cause the Saint’s body to self-destruct. This was more of
a self-defense instinct than magic, since when they were babies, they controlled
that power without knowing anything about magic.

However,

(…Acqua, he doesn’t have the limit of being...a Saint…?…That power…has it
already overcome what…a human can already control…?)

Needless to say, besides being a Saint, Acqua had the power of God’s Right
Seat. The reason for him to be called Acqua of the Back was because he had the
element of the Archangel Power of God. Normally, one would think that it was
just a natural addition of power, but in reality, this increased power doubled the
burden on him.

Yes.

What was amazing was that Acqua had already controlled 200% of that power
and still hadn’t gone amok, his facial expression not changing at all.

(…That’s impossible. This isn’t something that can be excused through a word
like ‘quality’ or ‘genius’. These two incompatible elements of a Saint and God’s
Right Seat are both in the same body. This is already impossible on its own…)

This term called ‘talent’, it was a forceful yet acceptable one.

But this was different.

Since Kanzaki was within this level, she understood.

Talent, ability, these terms weren’t such convenient things in reality.

(…Is there anything…)

Kanzaki heard a small sound.

It was the sound of Acqua of the Back standing in front of Kanzaki.

(…Saint, and God’s Right Seat…)

Seeing this strong opponent in front of her, Kanzaki pondered.

(…Why must these two powers coexist in such a place…!)

- Toaru Majutsu no Index Light Novel Volume 16 Chapter 4 Part 2