Update 3: The problem has since been fixed, and users should finally be able to play without an active internet connection.

Update 2: According to Konami the requirement is a bug. The publisher is currently working on a fix, even if no estimate has been given for its deployment for the moment.

We are aware of the offline play issue for Metal Gear Rising for Steam and are working on a fix. Please stay tuned for more updates!

The original article can be found below:

Metal Gear Rising: Revengeance has just been released on PC and reports are starting to appear about the game requiring users to be always connected online to play.

The title will not start if Steam doesn't detect a connection to the internet, and will quit to desktop if the said connection is interrupted.

At the moment we don't know if this is intended or a bug (which is possible, since most always online DRM at least give you some kind of message when they detect that your internet connection is cut, instead of just quitting to desktop), but there's absolutely no warning about any always online requirement or similar DRM on Steam's store page.

Update: according to NeoGAF user Guess Who the online requirement is caused by the way Metal Gear Rising uses the Steam API, and utilizing a modified steam_api.dll file allows it to work in Steam Offline mode. While this still doesn't say if it's a bug or an intentional implementation, it indicates that the issue would be easily solved if Steam or Konami were to take action on it.

We have contacted Konami for a clarification on the issue, and we'll keep you updated if they'll share anything relevant.