Binary for windows (Cross compiled from Linux, tested with wine): http://dev.pulsir.eu/krofna/llkrof.exe
Source (as before): https://gist.github.com/krofna/10605563/
This time it also has repacking support:
To unpack: llkrof.exe x File.arc
To repack: llkrof.exe Folder
It also decrypts .WSC files from Rio.arc now. Text strings are there (ja_JP.SHIFT-JIS encoded, file is binary).