Thanks to sleuthing friends around the world, the mystery of the glass negatives has at least been partially solved, and its more interesting than I could have hoped for.
One friend, Chiharu, said that the girl on the left on the third photo is wearing a typical Japanese school uniform, and the person in the seventh photo is dressed for some kind of farm work.
The plaque identifies the young man as the winner of the Odaka Youth Speech Contest at an event held by the Odaka City Crime Stopper Association. At the bottom, it says, “Given by Youth Association of Chita County, and Prefecture Assembly Member Isao Mori.” According to Chiharu, Odaka is now a part of Nagoya city, Midori-ku.
However, another helpful translator read the town as Odako-cho in Aichi, not Chita (or Chiba), and the name of the assembly member as “Isamu” not “Isao.”
This raises the question of what a Crime Stopper Association is and why it was necessary in Odaka (another friend translated it as “anti-crime assocation”). In any case, if anyone has more info on Japanese crime stoppers of the 40’s, or has some ties to Odaka, please do tell me more.