All of the text that's relevant and meant to be seen by the player is stored in romfs/message and the files (ending with _LZ.bin) are LZ10 files containing 2 directories, ArcBase and ArcVoice. I only edited ArcBase but editing ArcVoice will theoretically make the voices say (well spell) English. You can decompress the LZ10 files with EveryFileExplorer then open the in Karameru where you can compress them and edit with Kuriimu. In most if not all areas, you can simply copy the text from the North American version. However a few things need to be translated. You can decompress the source games and my Github release and take a look.