If it "reaches cobol" then it is still there after the UNSTRING.
You will not see Chinese characters unless you are using a Codepage which understands Chinese characters. You will see byte-values. And, probably, you won't see the byte-values because they have no display value in the Codepage you are using.
Try DISPLAY of the field from the Cobol program, and then use HEX when you display the output.
If you think a program which displays in hex from Cobol might be useful, then you can search for BBHEXD, aka The Junkbuster, on the sister-site http://ibmmainframes.com