Probably a cicada of the genus Meimuna, possibly Walker’s cicada, Meimuna opalifera which is commonly found in Japan, Korea, Taiwan and Mainland China. They feed on the sap of trees and are harmless and are believed to live for a total of 2 – 3 years.
In Summer they can be very loud due to their large numbers. In Japan they are commonly called “tsuku-tsuku-bōshi” due to the sound they make.
Further reading:
https://en.wikipedia.org/wiki/Meimuna_opalifera
https://www.uniprot.org/taxonomy/179424
https://www.cicadamania.com/cicadas/category/genera/meimuna/