cell9 creator of NTR CFW for the 3DS, has released a language emulation plugin for it, here is a quote from the source:
The language emulation plugin can solve the language issues which made some region-locked games failed to play in NTR mode, for example, Zelda Majoras Mask.
This plugin could also be used switch languages for games that have multiple language files. For example, the USA version of CRUSH 3D will display Japanese language when it was run on Japanese consoles, and it could be switched to the proper language by using the language emulation plugin.
1 find the plugin file you want (langemu_cn for Simp.Chinese, langemu_cht for Trad.Chinese, langemu_jp for Japanese, langemu_en for USA, langemu_en_europe for Europe).
2 copy the plugin file to plugin\TITLEID on the sdcard, for example, plugin\00040000000D0000
3 start the game and it will emulate the language automatically.
I have already made folders for several games including Majoras Mask eu/us in the package.