In the game, players control a human child who has fallen into the Underground, a large and out-of-the-way place under a mountain, separated from the rest of the world by a magic wall called the Barrier. The player meets many kinds of monsters as they try to return to the surface, mainly through the fighting system; the player takes turns selecting actions and avoiding attacks made of many bullets, and can choose to befriend or subdue monsters so that they won't get killed. The player's choices change many things in the game, including how characters act, and what kind of story it is.