When I visited one of my friends who works for the farm, she gave me some kuwa-no-mi, the mulberries picked from the mulberry tree there.
You can see the mulberry jam at the grocery store or supermarket, but not so many mulberries fruits themselves.
In Japan, they say "the taste of mulberry is the taste of the first love."
Often, sweet & sour taste is described as the taste of the first love in Japan.
I think it's because the first love usually does not go well as they expected because of their lack of experiences. So, they tend to make some mistakes. By remembering those mistakes, they feel little sad, sometime it even makes them cry. When you cry, you feel some stimulation on your throat. And that stimulation is the similar stimulation when you have something sour. So, that's why people say "the taste of mulberry is the taste of the first love (sweet & sour,)" I think.
My first love was when I was in the kindergarten, and she was one of the teachers there;
It's some decades ago.
...O, well. I just have the mulberries.