Native dual audio / Japanese voice support

Yes, DDDA Japanese VoiceOver Project mod[www.nexusmods.com] exists, and it's even linked here among other guides, but there are a couple problems with that mod:

1. As outlined on the mod's page, some of the pawn & NPC voice clips are still English + background voice clips in some of the cutscenes are English, and the FMV played after the Tainted Mountain events is the English version as well
   
2. The mod replaces the game's data, so disabling it or switching between the audio languages back and forth is a hassle

Meanwhile, the copy of the game purchased off the Japanese Steam store comes with English and Japanese audio languages right out of the gate, complete with voice language setting in the main menu. However, getting a hold of the Japanese PC version of the game is also highly inconvenient if you already own the regular version of the game (and even if you don't, it still involves region switching or secondary accounts shenanigans).

So, here's the JP-exclusive extra data and a simple config edit to expose the hidden setting for you.

Grab it on the Internet Archive[archive.org] (DDL[archive.org]) – 1.4 GB

Copy over the contents of the archive into the game's directory, then open the ...\Steam\steamapps\appmanifest_367500.acf config with a text editor and swap its "InstalledDepots" section for this one:

※ In case your appmanifest_367500.acf edits don't persist:
- Try exiting Steam completely before editing the appmanifest; after editing the file, set its file properties as read-only.
- If the other option fails anyway, try launching the game via its executable directly instead of through Steam's UI.

That's it, all done. You can now toggle the voice language in the main menu.

Q: But what about the Japanese version of Coils of Light?
A: It's not featured in-game in the Japanese editions of modern DDDA re-releases, and it wasn't included in the original PS360 Dark Arisen release either. The game's Japanese OST & the Masterworks Collection OST don't have the Japanese version of the song, too.
※ It'd be easy to put together a mod that replaces the BBI credits roll theme and the looping version of it that plays during the boss fight with Daimon in his first form (the currently available mods for this have issues), but I can't procure a high-quality source for the reencode to be on par with the English version.

Full credit goes to Mataki952 for providing the JP-exclusive data!