There is only one file type that uses the .MGA extension:
Document used by Manga Reader, a program used to read Manga comic books and print cartoons; stores a compressed archive of the document pages, including pagination data, text, and graphics; used for distributing manga electronically.
MGA files are .ZIP archives that have been renamed with the ".mga" extension. Therefore, you can decompress them with any ZIP decompression utility.
NOTE: Manga documents can be created using the Manga Creator program that is included with the Manga Reader installation.
Updated: February 5, 2011