Since all the files are stored in the same area, it would hard for me to pinpoint you in the right direction since I'm awful at explaining things. So, I can show you instead! At least, I hope I can explain things
with pictures properly. This is on my legit New Game+ file, so pardon the
lack of fangs.
Here is a screenshot of my file before I've edited it.
Before we start, do keep in mind that the way the bytes are stored are stored in little endian. And, as usual,
be sure to make backups! On my file, I currently have 511 Demon Fangs and 4,172,087 Yen. Since 511 is
01 FF it may yield similar results, so it's best to search for your money first unless you don't have a high amount. So, the current value for my money is
3F A9 37. Since I got no results initially, I added an extra
00 to the end and there it is. And the highlight section is where your money is. Keep in mind how it looks—it is backwards. Now, when you ease down a bit you'll see FF 01. And this is the value for your demon fangs in little endian!
And if you're going for max fangs, the value would be
27 0F. So, all you need to do is edit the FF 01 to 0F 27. The red square is the money while the purple is the edited demon fang value.
All you need to do is apply and save changes the edits.
So long as you did it right, you should wind up with a total of 9999 Demon Fangs!