Despite being the sixth game in the series, Atelier Iris: Eternal Mana was the first to come West.
The exact reasoning behind this isn’t entirely clear, but it may be something to do with the fact that the early Atelier games were primarily abstract management simulations with RPG elements, while Atelier Iris unfolds in a manner much more like what the Western audience would have understood “an RPG” to be in 2005.
Perhaps it was assumed the West wasn’t ready for that sort of thing. Perhaps the amount of text in the earlier games made them impractical to localise at the time. Or perhaps they just sort of fell through the cracks. Whatever the reasoning, Atelier Iris: Eternal Mana was the West’s first Atelier game, so that’s where we begin our journey.