She had once read in a book about consciousness that over the years, the human brain makes an AI version of your loved ones. The brain collects data, and within your brain, you host a virtual version of that person. Upon the person’s death, your brain still believes the virtual person exists, because, in a sense, the person still does. After a while, though, the memory fades, and each year, you are left with an increasingly diminished version of the AI you had made when the person was still alive.
She could feel herself forgetting all the details of Marx - the sound of his voice, the feeling of his fingers and the way they gestured, his precise temperature, his scent on clothing, the way he looked walking away, or running up a flight of stairs. Eventually, Sadie imagined that Marx would be reduced to a single image: just a man standing under a distant torii gate, holding his hat in his hands, waiting for her.