I'm not a mod so it ain't my call, I'm just making an observation.
Anyway, I was intrigued so I spent an hour looking into the game. Here's a few things I discovered, which may be useful for anyone who has a go at it themselves. (I did all of this before I noticed Velek's post above mine, so it may repeat a couple of things. Still, this is what I figured out in the last hour or so.
The graphics for the text are 2 BPP and the first kanji is stored at $5DC86. The game, for some reason, takes the values stored there, then does an EOR #$FF before putting it in RAM for a DMA transfer to VRAM. No idea why they need to do the EOR instead of just putting the actual value, but whatever.
The table reference to $5DC86 is at $58F2A. Ultimately, the reference to this address comes from $117F6B, where the C2 there is doubled then added to a value stored at $585A4, but that's not important right now. What IS important is that the C2 refers to that particular kanji, and another look tells me how the text system works.
Before C2 is FF, and FF tells the game to use kanji bank 3, if you like (the game checks for FD, FE and FF). If the address is under FD, it signals the primary bank, where the kana etc is.
It's at this point that I realise this is just for the character name: in this case, 博士 [hakase] or 'doctor'. Before the name, there's a byte saying how many bytes to read - in this case, 04, because it's FF C2 FD 67 (two kanji). The actual text is another matter.
Making a table file for the basic kana is trivial at this point, and a quick search for the first two characters bring me to $60000. Yep, that's where the text is stored. A little fiddling tells me exactly what's going on. It starts with 03 FD E8, which tells the game that this is the aforementioned doctor speaking. If I change it to E7, the name changes to Charles. I haven't delved into the meaning of 03 FD, but if you change FD to FE, you get a different kanji, so who knows for now.
With some messing around, I had enough information to make a simple Romaji table file. Whoever wants to give this a try can replace what's there with Shift-JIS or what have you. Here you are:
So that's as far as I've got, but really, anyone with some small ROM hacking ability can go to $60000 with this table file and get to work. I haven't documented some control codes in the $00-$0F range, so there's more to be discovered, but it looks like the system is pretty straightforward.
Hope this gives you a start!