CGs can be found in the 'evt' folder. There are sub-folders with names named "evm_#" with the # being some number.

'cg' contains the graphics of the CG. Compressed with LZ77-2 (0x11 header). 'cl' is the palette. Uncompressed and extremely easy to manipulate. 'sc' contains the TSA (also compressed using LZ77-11).

Images are 256x192, covering one of the screens (typically the bottom one, not that it matters).

See a guide on editing CG, CL, and SC files to learn how to hack Cutscene Graphics.

