1. Extract ARCV0.BIN and ARCVINFO.BIN from your game
2. Extract those two .BIN's with the unpacker
3. In the \Unpack\Keep\ Folder, replace the LanguageKeep_jp.res with your own
4. Insert the edited (You can check by comparing size or the date since it was last modified) ARC0.BIN and ARCVINFO.BIN...