Chocobo no Fushigi na Dungeon for WonderSwan

It begins with another chocobo finding a crystal in a garden and being turned evil by it. The evil chocobo kicks the player's chocobo down into a dungeon, and that is where the adventure starts: navigating an ever-changing dungeon that rearranges itself between visits, collecting weapons and items to fight increasingly powerful enemies, working toward the confrontation that can undo what the crystal did.