unpack school days VN .gpk files

[bagusix]

hello, i want to unpack (and repack) files from school days games.

 

This files are .gpk file and may be the game (school days) use ADVSystem engine.

I try to unpack with crass software and for gpk file crass say that the engine is ADVSystem (ADVSystem    .GPK weak magic: .PK .TPK .WPK .MPK .PK0 .PKA .PKB .PKC .PKD )

but crass can not to unpack the files.

thank you in advance, my goal would be to translate the game.