Have you already tried this script?http://aluigi.org/bms/arslan.bms
Another alternative, in case that doesn't work, is http://aluigi.org/bms/dynasty_warriors_4.bms
Tried out both scripts. I had to modify them slightly and remove the line for IDX files because this game doesn't have one.
arslan didn't do anything and stopped before anything could be extracted, and the DS4 script extracted a little bit before it stopped due to not being able to read after a certain offset (the coverage was at about 1%)
All of the .dat files it pulled don't work, but a few .dc5 and .fnc files did get pulled out, but I have no idea what to do with them.
I also got a few .txt files, but they were all garbled and unreadable.
I've tried other scripts for KT games in the past but none of them work because I'm pretty sure each game is unique in the way it stores and compresses things, which makes it impossible to get into the files unless you write a script specifically for the game you want to get into. :\