A noble beginning that fails to satisfy on its own.
Fire Emblem: Fates primarily comes in two distinct flavors, Birthright and Conquest, though the game expects you to play both, as well as the third follow-up DLC campaign, Revelation, as a matter of achieving full completion of the story. This is Fates' best and worst quality, since it makes for a stronger larger story over the course of the three interconnected titles, where the sum is greater than its parts, but the parts are being sold as individual game experiences (unless you simply purchase all three at once in the Special Edition).
Fates as a whole has amazing production value especially for the 3DS. Its lush, albeit infrequent, cinematic scenes are a joy to behold, and the animations in the game are tight and fluid while remaining true to the series' history of unit attacks and counters going back to its pixel-art days. On a technical level its precision and quality is at the highest level, where you can just feel the effort and love put into the game and its two siblings.
Fates' problem of feeling like a single game divided into three parts is the most prevalent in the case of Birthright—clearly intended as the first story of the three—which has the most straightforward version of the story, as well as the most straightforward and uncomplicated gameplay. In all three variants of the game, you start off the same for the first six episodes until you have to make the pivotal choice of choosing which side you want to go with.
Raised and protected in a castle as a prince/princess of Nohr, a warlike nation, your customizable player character, Corrin, is tasked by the King of Nohr to go on a mission. During the mission you wind up in the arms of Nohr's rival, Hoshido, where you learn you are actually a prince/princess of their royal family who was kidnapped by Nohr after the death of the former king at the hands of the ruthless King of Nohr. When both royal families meet on the battlefield, the player must choose between their Hoshidan family (Birthright) and their Nohrian adopted family (Conquest), or—when the DLC drops on March 10th—going your own path (Revelation). The main path you haven't chosen (provided you haven't bought the $80 Special Edition that has them all preloaded) will be available as DLC content for $20 at the time of choosing if you decide to follow a different path.
Birthright's choice, to side with your birth family against the King, feels like the most natural choice, once the nature of the peace-loving nation is revealed, which fits with the simpler gameplay and story that follows in Birthright. Upon making the choice to side with Hoshido, a nation based on Eastern/Japanese art and influences to Nohr's Germanic/Western medieval ones, the narrative follows a particularly straightforward path as you chart a course of action repelling Nohrian invaders and finally taking the battle to the enemy king himself. Along the way you are guided by a former Nohrian princess, Azura, whose magical singing works as a kind of deus ex machina to get the characters out of trouble whenever the plot thickens too much against them.
Much of Birthright's story doesn't particularly make sense, with your Nohrian enemies at times seeming more willing to throw themselves on their swords for you than to actually fight against you. Martyrdom seems to be a major feature on both sides to the point where it becomes almost silly. While the game does follow a somewhat traditional animé-esque plot of "Good Guys Versus Good Guys Who Just Happen to Be on the Wrong Side™", this gets a little bit obnoxious towards the end as no one on either side seems to have much in the way of self-preservation. When a character—on my own team who I had been trying to romance with the main character—died in a moment of self-sacrifice by falling into a bottomless chasm, a pegasus-riding side character's dialogue mirrored my own feelings of the pointlessness of it, "I could have saved him."
Now, I mentioned romance. Like prior Fire Emblem games, the combat system allows characters to back each other up in combat. When this happens, it increases their individual affinity to each other; and if this happens enough, the player can on a submenu introduce dialogue options between characters that increases their bonds, making them more effective fighters but also intensifying their emotional relationships. In male/female relationships, this can eventually result in a marriage option where the partners have children who, owing to alternate dimensions known as "deep realms," are immediately full-grown and can join you in combat as playable characters after you meet them in special side missions known as "Paralogues." Though Fire Emblem Fates gives you a binary gender choice for your character, you can't choose to romance (or have other characters romance) characters of the same sex.
As a tactical RPG, Birthright is both deceptively simple and mind-numbingly difficult. Earlier games in the series, like the GBA Sacred Stones which is a great example that's available through the eShop, were fairly relentless with their implementation of the permadeath unit mechanic, and levels and combats were designed to accommodate the precious nature of each character's unique skills and abilities. Making tactical decisions were a risk-taking exercise in determining if your characters would or wouldn't be wiped out.
Birthright, whose default settings are a casual option that brings characters back to fight in the next battle, has clearly been tuned for this expectation, making combat much more straightforward in the matter of bringing a large and strong enough force to brute-force your way through most combats. With permadeath turned on, especially towards the end-game, it might be so difficult as to be ridiculously frustrating, as the higher-level enemies seem designed to take out as many characters as possible.
Birthright has a meta-game base-building mechanic (on the timeless astral plane, owing for how you can have children but continue on with the story) where you build the shops you make purchases from between levels, as your characters level up. The bases can also be visited by other players, or to grind you can invade other player's bases for experience and money (and they yours). Another way to grind is by purchasing "challenge" encounters on maps that you've already completed, and by doing so is probably the only way you can max out all your character's relationships. Between missions you can also increase the bond with the character you are married to, and invite other characters to your room to increase affinity with them, while they stammer and get red in the face (for real, not a joke).
All in all, while the relationship-building is fun and the base-building provides a fun diversion and way to create challenges for other players, at its heart Birthright is the beginning chapter of a much larger story, while at the same time trying (and failing) to be self-contained. Birthright, especially after having put significant time into Conquest and a small amount of time into Revelation, feels necessary to the overall complete alternate-story arc, but it's an entire game built as a "bad ending," where no matter what, it feels unsatisfying in a way that's meant to draw you on to the other variants to try their scenarios.
In that sense, as a stand-alone title Fire Emblem: Fates: Birthright is not a particularly good game, though it's not a bad one either. It's an above-average tactical RPG with excellent production value and moderately good gameplay scenarios, but it feels surprisingly one-note and dissatisfying if taken on its own merits as a self-contained game. If you're willing to pony up the extra $20 to buy Conquest, or the $80 price tag of the Special Edition with both Conquest and Revelation, I highly recommend it, as the whole experience of all three is where the real value of the game is.