> I have tested your source by installing NotoSansCJKkr-Regular.otf etc.
> It seems to work OK.
> Note that I'm using  ".otf" fonts, not ".ttf" ones.
> I attach cjkkrtest.tar.gz in which there are k.tex and k.pdf.
>

Your output is perfect.
But I still get an error message which is as same as Luigi mentioned.
Would you please send K.log file to compare with mine?

>
> luatex crashes with error message
> mtx-context     | fatal error: no return code, message: latex: execution
> interrupted
>
> Under WINE (linux) mingw 64bit,
> luatex.exe
> Version beta-0.79.1 (TeX Live 2014/W32TeX) (rev 5041)
> is ok
>
> luatex.exe experimental is also also ok and both give the same result of
> u.pdf

My version of latex is
This is LuaTeX, Version beta-0.79.1 (TeX Live 2014/dev) (rev 4972)