"I- you- Augh! Don't stick your hand into things you don't know what are! That's what random debris is for!"
Derek Covered his face with his hand for a moment, then sighed. "At least we know that whatever is on the other side isn't immediately lethal, nor will it do a portal cut. Next step is peeking through it, I guess. If I start acting like something on the other side is pulling me in, pull me out."
Let's take a look-see. Head only.
Derek sticks his head in as Gaia, Akihiro and Undine stand back. Akihiro readies himself for the distinct possibility of Derek being pulled in. However, instead of being pulled, he finds himself voluntarily trapped by the mesmerizing display he sees.
A vast expanse of civilization: incredible architecture, infinite attention to detail, the laughter of children and the growls of beasts. Towers with glass windows, market buildings and walled-off bath houses. And every single inch of it is painted blue like someone took the largest bucket of blue paint in the universe and poured it over a city.
Then Derek sees the one thing that finally gives an explanation to what's happening in this school. Or, to be more precise, many things.
Demons.
Demons everywhere. Mythical hounds, three-headed birds of prey, humans with snake tails. Every single person and creature in the grand blue city is some form of otherworldly entity, and they've got a direct gateway to the basement of Hiramasu Academy, and by extension, Earth in its entirety.
How long has this been here? Why did no one notice it before? And why are the demons in the streets of the demon world apparently ignoring it, going on with their normal activities as usual?
(GAIA): "Hey, what is it? What do you see?"