Despite being the sequel to Final Fantasy XII, Revenant Wings is actually not an RPG. It's a strategy game, much like Tactics or Tactics Advance, with bite-sized missions and fairly small battlefields. Each of these missions comes with an objective and win condition, and completing them will further the storyline. It's not necessary to complete all of the missions to finish the game, but each one offers a useful bit of information about the plot, and completing extra ones will let your party acquire rare items and summons. Once you accept a mission and learn your objective, the screen will change and the strategy process begins.
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In short, the new battle system is both engaging and challenging. Fans interested in importing the game should know that the game is heavily text based, so if you don't understand Japanese you're going to have a hard time following directions. There are some visual demonstrations to help you out, but it's just easier if you can read the instructions instead of learning the battle system through trial and error. Although since you have option of starting a mission over should you fail, intrepid non-Japanese speakers may decide that trial and error is good enough for them.