Metal Gear Solid V: The Phantom Pain will be divided into two parts: the prologue, Ground Zeroes, which takes place in 1975, and the main game, which takes place in 1984. Sound confusing? It's actually done that way to make it less so.
In a one-on-one interview with Weekly Famitsu, Kojima talked about the reasons to have Ground Zeroes be separate from the main game. "I think if players of the previous Metal Gear Solid games are immediately thrust into the open world of the main game [of MGSV], they might find it confusing." Kojima explained. "Simply put, the main game world is vast. And you have no idea from where enemies will target you. As time passes, the game's reactions change depending on the player's actions. So much so that it's hard for us on the development side."
According to Kojima, Ground Zeroes is there to acclimate players to the new open game style. Both time and the weather are fixed, but the world is otherwise open, giving players a chance to get used to the fluid nature of being able to carry out missions any way they want to.
"A lot of people seem to misunderstand when I use the term 'open world' -- [MGSV] is not a game where Snake spends a day fishing or changes jobs and leads a different life." Kojima said about the open nature of the game. "The field is open world, and you are free to do what you want, but your objective in MGSV is clear cut."
Kojima stated that he wanted to focus on the "tactical" part of the "tactical espionage operations" game, such as studying maps, planning routes and preparing equipment for the upcoming mission and then carrying it out. "It's like taking an entire mountain and using it to play a survival game (Editor's note: Think paintball)." Kojima explained. "In survival games it's fun having shootouts, but it's equally as fun to set up tactics like choosing teams and planning your attack. That's the sort of play we're aiming for in MGSV."
Kojima did also note that the user interface would be slightly different for Ground Zeroes and the main body of the game, but would not elaborate on exactly what would be different in what sort of way.
The main themes of Metal Gear Solid V are "Race" and "Revenge". Kojima did have this to say about the story for MGSV, "At the end of Ground Zeroes, something terrible happens, and that leads to the main game. Why is the theme of MGSV 'Revenge?' You'll have to play Ground Zeroes to understand. This is the hypocentre -- in other words, the 'ground zero' of Snake's story." Oooh. Cryptic.
Metal Gear Solid V: The Phantom Pain is scheduled for release on the PlayStation 3, PlayStation 4, Xbox 360, and Xbox One, and it can't come out soon enough.