There are two kingdoms at war, the peace-loving Hoshido and the glory-seeking Nohr. It's up to the Player to decide which side to take. As always, there are two sides to every story, and in this game the path you choose ultimately decides your characters fate. No matter what, the world and characters will be the same, but depending on the decision you make, the storyline, the battles and outcomes will be drastically different.
On the Hoshido side, you will experience a more traditional path as you work together with your allies to fend off nohrian invaders. Because this path's story is more similar to pas Fire Emblem games, it's a bit more accessible - even for newcomers. On the other hand, if you choose the Nohr, you will be forced to revolutionize and unrule the kingdom from the inside. So the story will be slightly more complex and the difficulty will be more challenging.
The new Fire Emblem for Nintendo3DS is planned for a 2016 release for North America (and Europe). Stay tuned for more information in the future.