One of two things is happening in the opening scene of the first episode of Devilman Crybaby.
- The end of the world. Heaven is literally raining down on Earth, and all the sin and demons are being purged, leaving Earth a molten husk. The End.
- This is The Fall of Lucifer (or something along those lines).
The former is obvious and expected. This is what will happen if things don’t go in “our” favor. Whoever the hero is loses, humanity fails, etc. This is what we’re avoiding.
The latter is far more interesting. The way I take it, Earth was already some pristine planet billions of years ago. The life on it was horrifying by our standards– all monstrous and deformed and terrible to behold– but it was the way life developed before (the) God(s) interfered. The angels fall from grace, and their arrival destroys this ancient Earth, but the now-devils take the forms of these creatures from prehistory and hide away as life begins anew.
We as humanity are a product of the apocalypse. In natural history, countless species have gone extinct in order to pave the way for us to evolve and find our niche on Earth. In mythology and religion, we’re often the descendants of the survivors of some cataclysm– be it a flood or whatever. Our spirituality is filled with stories of new gods overtaking old gods and proclaiming themselves to be the true gods– patricide begets patriarchy. Even when our histories disregard prior belief systems, we take the imagery of the old systems and turn them into the evils lurking in the darkness.
Our devils are usually just remnants of a past we wish to divorce ourselves from, lest we acknowledge that which suffered to bring our prosperity as a species. If that’s the case, making the hero of the story the pinnacle of those past “sins” would be perfect.