Corpse Party PC (GoG/Steam) Extracting from unknown file type help?

[Newbcrypter]

Corpse Party is a fairly neat little horror game, and for a few reasons, I would like to rip some Graphics/SFX from the game.
Unfortunately, the files that seem to contain what I want are in the .BCX format, which after some googling, appears to only be used for this game.
I have absolutely no idea where to begin with this, so I would greatly appreciate some help!

(Here's one of the files https://www92.zippyshare.com/v/wrxbP7PO/file.html I'm talking about.)

P.S.
I have no experience in decrypting

[aluigi]

It's the same encrypted DX format used in other few games apparently without the same developer in common.
I have just updated the script for implementing the key of this game:
http://aluigi.org/bms/heart_of_crown.bms

I didn't know that the game used this format, I simply found some repeated 12bytes sequences of same bytes (the "pattern") and tried to test them as xor key, found the correct one after 3 tries where a sequences of 0xaa appeared in the output file since there are no sequences of zeroes available (original bytes XOR 0xaa = key). I noticed the DX at the beginning of the file and searched it in my scripts database where indeed the format was already covered.

[AdPro]

Is there an encryption key for this script? I'm trying to mod the game's VN art. Whilst using the reimport feature, I can't seem to get the modded PNGs back into the BCX file.

EDIT: NVM, I was stupid, I didn't figure out how to use the reimporter! I figured it out now