How to modify the GRP and MDT files?
And I can't find th01's title image
.MDT files are the game's music files, so there is really no need to modify them.
.GRP files are essentially .PI files, just like the ones found in other PC-98 Touhou games. To edit those, you'll need a hex editor and ViX.
1) Open GRP file with a hex editor;
2) For comparison purposes you can open a PI file from any other Touhou game with a hex editor;
3) Change the first 12 values of the GRP file (ZN PC98 / 5A4E1A000000000450433938) to those of the PI file (Pi WIN* / 50691A000000000457494E2A), save;
4) Change the file extension from GRP to PI;
5) Now you can convert the PI file to PNG format with ViX and edit it;
6) After editing, convert the PNG file back to PI, open the converted PI file with a hex editor and change the values at offset 0x5 from 0101 to 0000;
7) Change back the first 12 hex values from step 3 (ZN PC98), and change the file extension back to GRP;
Replace the GRP file with EditDisk and run the game to try it out.
The main title screen is located in REIIDEN3.GRP.
By the way, I managed to fix Kongara's Siddham characters, so if you want to use those in your patch, feel free to add them:
Download.
