Soul_Caliber
Now I will tell you what I understand, hope it helps. Leo and Kaguya are either in a parallel universe or a fanfic universe right now. As a result of the attack on Earth, corruption increased tremendously, disrupting the overall balance and order of the world. For Leo and Kaguya Leo is a conceptual being, this world where concepts, space, time, almost everything is unbalanced affects him a lot. For example, if there was a conceptual time entity instead of Leo, there might even be a possibility of receiving permanent damage due to the constantly changing and unstable time. And the corrupt world is about to spiral out of control, and outsiders seem to be attacking Kaguya and Leo. Why is Kaguya here? Kaguya cares about Leo and Kazuma no matter how much they fight, the same goes for those two. If you saw the #harem part in the tag section of the book, you can understand it a little. In short, Kaguya is here both because she's worried about Leo and to make fun of him. This is what I understand