This picture is "ume-boshi".
Ume is a plum seed, umeboshi is dry plum in English and it have strong acidity taste.
Ume-boshi is a kind of pickles, it is made to confit salt after drying harvested plums.
It can preserve long term over 100 years.
Almost Japanese know thats acid taste so when we imagine umeboshi we secrete saliva naturally like a Pavlov's dog.
In the picture you can see some black parts, that are basil leaves to enhance flavor and color.