While many unmanned stores in Japan are in rural areas that sell veggies, there are some located in urban areas like this one.
An unmanned store is called Mujin Hanbaisho and is basically a shop where you are trusted to take an item and leave money for the owner who is not around.
This particular unmanned shop is in my neck of the woods - the Ebara/Meguro part of Tokyo.
The tub on the left says "anything inside here is 10 yen" while the basket on the right says "Ageru" which means "I give you (for free).
A closer look at the table which has various bits n bobs priced up to 1000 yen. You can see a small wooden box on the table with a hole in it which is where you should leave the money to pay for the item.
I didn't really take a close look at the table so not sure if they got change but there are places like this shrine that does actually have zennys for you to leave a larger note and take small change.
I didn't realize at the time until I read the notice on the door to search for "Sobarogu" which I did. It looks like they run a little soba noodle place - when they are not open, they leave stuff outside unattended for folks to buy.