The air they breathed was different from what everyone else breathed. It was thick and hot and constantly around them—them, and not any other soul, like the normal air consciously and constantly pushed their air—dirty and mean, asphyxiating and shallow—away. Only the two of them could smell it, outré sweetness and nauseating rawness; and only they could feel it, grinding and biting and stinging and somehow so ironically soft, and personal.
But it wasn't really air at all. It was not so much something their lungs yearned for (rasped for, when their bodies went too fast and hard for the world to keep up with,) but something that they forced into themselves, polluting like smoke and unwelcome like ash (a grimy coating in their lungs that refused to be coughed up). It turned their red blood into black. It was impossible to tell if they had been the first ones to exhale, or if it had always been there for them to inhale: like matter (or, all the more fitting, like energy), it was never created, nor could it be destroyed (a perfect parallel to their love).
Air—oxygen and then carbon dioxide, and then oxygen again—cycled and filtered and kept one's blood flowing to keep them from death; kept trees alive and forests growing. But this "air"—their dense, bloody cumulonimbus cloud, their destructive hurricane and lighting storm and howling black tornado that tore up trees and homes and uprooted the very fundamental meanings of love—it followed no cycle, and existed for no one's benefit. It poisoned them, killed them, with toxin so strong and fervent that they deemed it life.