Xak I & II is an enhanced version of the first two games in Xak series:

Xak - The Art of Visual Stage
Xak II - Rising of the Redmoon

More than just a compilation, this version was developed from scratch, featuring more detailed graphics, new musical compositions, voice acting, and new cut scenes, including a common intro for both games. The improved interface from the second game is now present during the first as well. Even though gameplay-wise this release is very similar to the originals, there are some slight changes as well: enemies are more aggressive, and sometimes appear at different spots than in the original. Although this release contains both games, they are treated as one long game, and it is only possible to start playing the second after having completed the first.