Chionanthus retusus

This is Chionanthus retusus. The Japanese name is Hitotsuba Tago, and generally called Nanja Monja no Ki, literally means 'some sort of unfamiliar tree'.

 

There are some different type of tress which is called "Nanja Monja", but I heard this is the most major one. So, this is the most familiar 'some sort of unfamiliar tree'. :-)

Done