Yangmei, also known as Yumberry is a Chinese fruit. The fruit ripens on the tree during the summer months, with a very narrow window of only a few weeks to ripen. The tree is an evergreen, with pale silvery bark and slender green leaves. It is a subtropical tree and is used for ornaments.
https://en.wikipedia.org/wiki/Yangmei
http://allfruits.blogspot.com/2013/08/fruits-name-starts-with-letter-y.html