Metal Gear Solid V: The Phantom Pain is the main story of Metal Gear Solid V: Ground Zeroes, released in March 2014. Set in a vast "open world" system, it explores the series' biggest mystery: why the hero of the protagonist falls into the evil path. In addition to the gripping story, it introduces the concept of time passing and weather changes, creating a "real infiltration simulation" with no specific strategy, opening the evolution of the true infiltration spy game.