Denji will get a breather when he finally stops breathing.
I think I remember the girl in question, not saying I recognized her, just that she saying all that I remember the moment. A girl shouting and crying for her parents, and I think that Fujimoto even drew the moment she stops and looks at Denji after Aki dies.
That is some amazing setup, not overly complex, it is just that most authors use background characters as only that... background, we rarely see any of them becoming something else. Generally when a "background" character does become important an author makes the effort of separating them from the crowd even before an event, which defeats the purpose a little I think