Kroman is ultimate Korean hangul romanization tool. It has a lot of implementations.
This is the emacs plugin.
Kroman emacs plugin is available at melpa,
You can install with emacs builtin package manager
M-x package-list-packages
C-s kroman
I
x
M-x kroman-romanize-region
M-x kroman-romanize-buffer
M-x kroman-romanize-other-window
Bug reports and pull requests are welcome on Github at http://github.com/cheunghy/kroman-el.
Kroman is available as open source under the terms of the MIT License.