Metal Gear Solid: Peace Walker

One day, Snake meets Ramón Gálvez, a peace teacher, and his student Paz Ortega, who ask for Militaires Sans Frontières' help in bringing peace to the country of Costa Rica. Recently, an unknown armed force has been causing trouble in the country due to its constitution forbidding a military army. Snake initially refuses to help, but after being presented with a tape recorder that he believes may belong to The Boss, he agrees to join the mission.

The game features a central mother base where players can save their game, develop weapons, and embark on quests. Players can replay previous missions to gain higher scores and participate in additional ones not necessary to the main story. Developing and upgrading weapons is done by spending currency known as GMP, which can be obtained by completing quests.