You're going to have to point out to me where exactly it insinuates that infinite universes can exist inside the Demon Realm.
The kanjis that was used for the
Endless Darkness is: Hate - "Limit", Naki - "Negation" and Yami - "Darkness". The container (also called crucible) which in turn referring to Demon World as you can see these two lines: "Darkness is the Demon World", "Light is the Human World".
Now lets get to your question here: "Where exactly it insinuates that infinite universes can exist inside the Demon Realm?"
Look at the panel again: "But even
in such a
world, there
was a line of
line of light"
. A clear example that it is referring to as a container given the sentence invokes the idea of a world that contains universes as a meager finite "
line" of light.
Soo look at this way... A world, as a container, is infinite, that sees universes, as a mere ray of light, which in question is your basic universe. Should be enough to assume
it is infinite in the sense that it can contain infinite amount of Ray of Lights.
It being called a "higher realm" just means it's of greater importance in the cosmic hierarchy. It does not mean that it is a dimensionally transcendent realm.
The entire point of the panel is to depict as something of a transcendent structure that sees a space-time continuum as a
finite line of light within its
infinite space and from a common sense,
a space-time continuum is not finite whatsoever.
That is without mentioning the cases where Demon World stated to
"overwrite" as well as
"consume" the reality of Human World. If we supposedly took two space-time continuums against eachother that doesn't mean one is going to eat away the other, they both have similar dimensionality afterall, no? Yet with such a structural quality, it was stated in DMC2 that
"Human World will return to Demon World". Human World, a space-time continuum, is a property of the owner Demon World, a container of such a property. That simple of a concept.
Infinite x Infinite is still Infinite. It does not justify being a higher infinite. It just means the Demon World is larger than the Human World and all the worlds it contains. But it does not mean it is dimensionally transcendent.
Take a moment and look at your reply again. At this rate, we are just nitpicking things out. Demon World institutes, an atleast, a
4th dimensional axis to
contain space-time continuums within it. The panel isn't specifically referring to a lower dimensional space like our usual 3rd one but Underworld in is entirety that
should be referring to that same
4th dimensional axis abbreviated as "Demon World" at the
very least.
Heck, on top, it sees an already
uncountably infinite structure according to your very "standards" as finite on top of itself claiming to be infinite in comparison to it. I hope this reply will help you to see the light otherwise I really can't do anything about it.