This is unlocked as part of normal story progression towards the end of chapter 4. After the chapter 4 boss encounter, as you leave, you will be greeted by a messenger. Agree to follow the messenger. As you make your way along a wooden bridges, the achievement will unlock just before you reach the next destination. Additional details in the spoilers:
*** Spoiler - click to reveal ***The chapter 4 boss fight occurs in the castle in the Amusement Park. After defeating the boss, take the elevator and exit the castle. As you are leaving, you encounter a peaceful machine who requests you accompany it. Accept the request and follow it. It will take you to the Machine Village. When you get close enough to see the Machine Village and the machines in it waving white flags, the achievement will unlock.