Its Final Fantasy VII trimmed down to fit on a 4 megabyte Famicom cartridge. Its an unauthorized pirate but a lot of effort seems to have been put into it. It is an original conversion, not just a hack. A few characters, a lot of dialog, a few land masses, and some features are missing. But, the overall story/script is preserved.
There are several interesting technical quirks about this cartridge. There is no CHR-ROM hardware/chip(s), rather the graphics (CHR data) are stored and generated from the two 2mb PRG ROM chips then transfered to a RAM chip at runtime. The RAM chip effectively replaces a CHR ROM chip. Also, the code is unusually linear, storing related story data, level data, conversation data and cut scene data in the same areas and chronologically throughout the ROM chips.
About Final Fantasy VII
2008-05-16 (updated 2013-05-31) #