Homebrew ROM Hack Puyo Tetris 3DS .dat file help

[BoxBoy7999]

I'm trying to make some custom Tetrominoes for Puyo Puyo Tetris 3DS, and I can't figure out how to get into the files. I have tried;
Puyo Tools (because the COMP file header)
Switch Toolbox (unsupported)
Kukkii (unsupported)
renaming it to puyo_beta.dds, and opening it in GIMP, (didn't work)
and I don't know what else to do.

 

[Colmines92]

Not sure, but the header "COMP" could be interpreted as COMPressed, then the next 0x11 could be related to lz11 compression.
Try removing the "COMP" part, then try to uncompress it using kuriimu2 's lz11 method.

 

[Aaaaaaaaaaaaaaa]

You can open it with kuriimu2 as a comp file after decompressing it with puyo tools