Now make a patch that completely erases any and all traces of Kaname Date. 😉
Boss should have been the main character~!
A downloadable patch for Windows
Playing AI: The Somnium Files in Japanese with English subtitles is a pretty well put together experience, with one pretty major caveat: the ending movie is presented in your UI language no matter what your audio language is set to.
While the English voice actors do a decent job, the transition is super jarring especially when unexpected. There seem to have been countless threads on the web about this issue, and while many of them suggest changing the UI language, none of the workarounds allow playing the game through and getting the original ending movie with English subtitles.
For that reason, I dug into the game files and discovered that it actually wasn't too complicated to swap out the file and make it play the Japanese version of the ending but leave the English subtitles displayed.
Much like the unpatched game, this does not follow your voice language setting, so to revert to English voices for the ending, the patch must be reverted. The easiest way to do so is to use "verify local files" in your Steam client.
Because the patch modifies files in the game directory whose names could well be considered spoilers, the patch is supplied as an XDelta 3 patch with a semi-automated batch script. Those who are curious and/or have finished the game already can of course read the batch file for the specifics, but to describe it without any spoilers, the files for the ending movie are stored in in a pair of UnityFS bundles, and the patch takes the Japanese version, renames it (and the file names inside it) to English, and replaces the English version of the file.
To apply the patch: