u/Xhinope

I'm interested in the Ys games, I've played 1 and 2, but ran into a bit of a snag while trying to find 3 on Steam. The next game with a number is 6? But there's Ys Origin, Ys Memories of Celceta, and Ys the Oath in Felghana. Are those supposed to be Ys 3, 4, and 5? If so, which one's which?