Preface: Attached image shows text editting and results and should be viewed before reading this.
So all the text is in Japanese Shift-JIS format and stored in plaintext and can be read with anything that supports Shift-JIS.
The very first line of the game "チャプター1のオープニングを見ますか?" is stored at the beginning of /romfs/data/chap1/chap1_scriptlist.MSG
From there you can open the chap1_scriptlist.MSG in a hex editor. It's actually really easy to replace text. You can actually overwrite the Japanese text with normal English ASCII right in the editor which is really cool. As you can see in the screen cap, new screens of text fairly consistently come at 128 character intrevals. So I guess so long as you fit the English text under 128 characters you wouldn't have to worry about offsets.
So along with the chap1_scriptlist.MSG which contains actual game text is
chap1_scriptlist.BIN
chap1_scriptlist.DAT
chap1_scriptlist.LST
I guess one of these contains the offsets.
And then I just used LayeredFS to get the editted cap_scriptlist.MSG into the game.
EDIT: Has it been confirmed that the 3DS version is coming stateside?
EDIT2: Attached the compiled layerFS plugin and the altered script for Chapter 1. Just put the 'plugin' and 'CPLayer' on the root of your SD and launch game with NTR.