American planes used to drop tiny pieces of what I assume are foils from air. It was to confuse the radar I'm told, but grownups weren't sure so they told the kids to run indoors if they saw shiny poisonous sparkles descending from the sky. Of course kids loved them, and rushed out to collect and stash them away in secret places. Mom did, even though she was in her early to mid teens.
Chocolates and cigarettes used to be wrapped in real foils when I was a child (not metal-treated paper like today) and Mom and my aunts were always super reluctant to throw away the foils, because they were metal and valuable, (metal got taken away to make weapons, but that's not unique to Japan,) but I think the sparkles from the sky was actually a happy memory for them. I used to collect my Dad's cigarette foils because they were the heaviest, and it smelled mysterious.
After the war, if you had friends in the occupying forces, and my uncle and his friend (for whom 45 years later I found myself working!) certainly did, you could get chocolates and silk stockings and American toothpastes. Mom and her aunts knew they were toothpastes, but the American ones tastes so good they secretly ate them, and used plain old salt to brush their teeth. In the 80's I used salt toothpastes, but they were scarce and terribly expensive and Mom used to laugh at the change of fashion. It's that Circle of Life again.