Metal Gear Solid: Peace Walker was out officially yesterday at Japan, unfortunately for North America would the 8th of June. I will be receive my PSP Metal Gear Solid: Peace Walker Premium Pack in another week. Peace Walker will be the first Metal Gear title for a portable platform directed by series’ creator Hideo Kojima. The story will take place following the events of Metal Gear Solid 3: Snake Eater and Metal Gear Solid: Portable Ops, which were both prequels to the original Metal Gear, and will once again star Naked Snake. Peace Walker’s original title was Metal Gear Solid 5: Peace Walker. The development team working on Peace Walker is as large as the team that worked on Metal Gear Solid 4: Guns of the Patriots.

Source from Wikipedia.