What you see above is a raw dump of the text, it needs some of the line ending stuff dropping to make it more readable.
Anyhow nearly all DS roms use Nintendos nitrorom file system, this means unlike nearly every other system individual files can be broken down into their components (there are however sub archives in a lot of roms varying from common like narc (search for narctool or read a few of the threads around here) to ones made by the company/game dev team).
That is besides the point, have a read of this thread to get an idea of the tools you can use and how:
http://www.sosuke.com/ezflash/viewtopic.php?t=457
Once you have done that browse to the \data\Japanese\Message directory (if using ndsts the data folder will be automatically loaded). Here will be a bunch of BMG files, open them in a hex editor. The first few lines after 20hex with read something like:
B006 0000 0002 0300 A807 0000 0002 0300
These are the pointers, they tell the game where sections begin/end. I have not gone and worked out how these ones work yet although if past experience with bmg files counts the chances are they are offset somehow ( 07a8 (hex) is 200 (hex) out or some such and how much it is out is usually related to the length of the pointer table or some such).
After this there will be DAT in the ASCII conversion, this is the start of the text.
From here I just pasted the text into a new file and viewed it in word (your hex editor should have a unicode option though), the chances are the section ends (00 hex) will want to be replaced to make it more readable, do not just do a search and replace though as 00 is also the start of a lot of roman alphabet stuff (see the staff.bmg file and you will see what I mean).