Don't worry, there is a "Backstory" option in the Metal Gear Solid V: Ground Zeroes menu which will explain and describe the story of the previous episode, Metal Gear Solid: Peace Walker. By looking at this, you will learn all about the background of Naked Snake, now known as Big Boss! We recommend that you play this amazing game as soon as you can in order to experience this stunning story, full of twists and turns!
In addition to the “Backstory” feature, while playing Metal Gear Solid V: Ground Zeroes, Kazuhira "Kaz" Miller, second-in-command of the "Militaires Sans Frontières", will tell you facts about the past through radio contact and you will also have to find Chico's Cassette Tapes scattered all around the map which will give you hints on what happened just before Metal Gear Solid V: Ground Zeroes. You’ll enjoy piecing the story together!