Nero is NOT a son of Sparda and has no demonic transformation (per se), but does have the demonic posssessed arm.
Something special about the grip of the Red Queen, nero's blade, that Kobayashi won't reveal yet. It has some sort of brake lever which does something...
Variel, the fiery demon boss you've seen is about the size of a small building, and just being near other structures, will cause them to catch on fire, so getting anywhere near close to him is a no-no
Nero, won't have a devil trigger, with the key word being 'Devil'. Some other kind of trigger?
Nero lives on the remote island of fortuna which is the setting for most of the game. He belongs to an order that worships Sparda and fight demons in his name. Nero does "Special jobs" for the order cleaning up "messy situtations".
That ends when a white-haired man in a long red coat breaks into the order's temple and starts slaying the high clergy. "Just because Nero's in the game, doesn't mean Dante isn't. Dante does appear.", Kobayashi admits.
In the ensuing cutscene, we witness a heated battle between the two demon hunters that includes all of the stylish sword swinging and acrobatic action one could hope for.
Dante, at first is the primary antagonist that Nero chases across Fortuna. Dante being playable is neither confirmed nor denied.