Ys I&II are left alone but also include a mixed mode called Eternal Story mode which interleaves the two games as one, you can also play them seperately. Ys III is said to have an "arranged storyline", which doesn't sound like a good idea when you look at travesties like the SEGA Classics Collection, although the game was simplistic in story at the time so it might not be a bad idea. Ys IV which is the most remade of them all has been redone in 3D. Ys IV Mask of the Sun - A New Theory, has been renvisioned from the SFC version of the game and not the PCE-CD version, I'm not familiar with this game so I don't know what the differences might be. Ys V doesn't appear to getting a remake at this time which doesn't make sense since that would have put all six games in the series together on one system.