Hideo Kojima shared a picture of a Metal Gear Rising poster that Kojima Productions received to color check. Two of the characters are hidden by a conveniently placed iPhone. Here’s the poster (click to enlarge):
It’s very likely one of those characters is Sunny from Metal Gear Solid 4, who has already been confirmed to make an appearance in the game, but hasn’t been unveiled yet. Only this silhouette has been shown so far:
Metal Gear Rising Revengeance releases in less than a month worldwide.
Source: Hideo Kojima Twitter