I don't see any structure.
What are the names of the other files in the game folder?
Sorry for the late reply!
There isn't really a folder because the .dat I previously uploaded (the one I need help with) was extracted from another .dat, start.dat, and I extracted it using Disgaea PC file manager, found in Disgaea PC tools ,and as I said, even though they're different games, some files are the same and so I was able to open start.dat with disgaea pc tools. They can be found here : https://github.com/ProgSys/pg_disatools
I uploaded start.dat here : https://mega.nz/#!l1oAgSDb!vepvI6Vnv2n5 ... OX32rc5QPs
I extracted start.dat from another .dat, SUBDATA.DAT,and I can't remember if I extracted it using a bms script or a software.
But, Disgaea PC tools CAN'T open this SUBDATA.DAT, even though Disgaea 1 PC has the same file. (So, they must have something different)
I uploaded SUBDATA.DAT here (of course the Disgaea 1 Complete one, the one that contains "start.dat", which contains the initial posted file) : https://mega.nz/#!RpwUiYIQ!j7TfxdEo83Wh ... YxEQ8d2PkM
Lastly, I extracted SUBDATA.DAT by extracting the game files from the nintendo switch .xci game file, by using hactool : https://github.com/SciresM/hactool
If you need any other information please let me know, I'll try to help as much as I can, and thank you again for replying me ^^