There are two Nier games actually, Nier Gestalt for Xbox 360 version and Nier Replicant for PS3. What's the different?
First, the hero's outlook
Nier from Nier Gestalt
Nier from Nier Replicant
Yup, both hero's name is Nier but in the Replicant version, he looks younger
Both Nier are questing to save a woman called Yonah from the Black Scrawl virus. The second difference is, Yonah is Nier's sister in Replicant, but Yonah is Nier's daughter in Replicant. Da wierd eh?
Extra note, there is a character called Kaine. Is is said that this Kaine is a hermaphrodite o.O
Kaine looks female in the screenshot, but she gained male “characteristics” after being possessed by a demon. This shows up in Kaine’s personality, which is described as masculine