Princess x Princess is the sequel/extension of Rishia's route from Shuffle 2.  Essentially, it begins with Rishia enthusiastically searching out extra wives for Raito while he has difficulty adjusting to his girlfriend's values.  However, this quickly expands into a game that, to some extent, can actually be called a sequel rather than a fandisc.  This is similar to how the original Shuffle's 'extras' functioned more like true additions to the original game than fandiscs.

I'm going to be blunt... this is better than the original game, to a significant degree.  A lot of the things I hated about how they handled Shuffle 2 are done differently in this game, and the style in general is much closer to how the original Shuffle was put together in terms of humor and character interactions.  For fanboys of the original Shuffle who hated or just weren't satisfied with Shuffle 2, this game is a saving grace.

That said, this game has the characters traveling to different parallel worlds, where they are inserted into their own roles (with varying degrees of memory alterations) in them.  In each, there are differences big and small (there is even one world where every character holds a near-perfect replication of the personality and role of a corresponding heroine from the original Shuffle), but the theme is mostly centered around Raito dealing with the issues in his own life using the experiences he has in these parallel worlds.  

The 'paths' in this game are either threesome or harem combinations with Rishia, based on how Raito takes in his experiences in the various worlds.  There is a threesome with Selena, Ai, and Lapis, with a full-on harem path and a Rishia-only path put in for kicks.  

For fanboys of the original, this game also succeeds in clarifying the 'canon' of continuity to this game from the original Shuffle.  The canon apparently is that Rin married Shia but died a significant period of time before she did.  

Kurogane Kaikitan part 1

Kurogane Kaikitan is the port of the Vita game by Minato Carnival.  It is a somewhat more action-focused game than is the norm for Minato Soft and its subsidiaries, with a much more serious subject matter.  The protagonist, Habaki Masamune is the leader of a student anti-terrorist task force using mystical weapons called Kurogane that manifest certain 'recorded' phenomena that can be controlled by the user (this is not explained on the official website, which annoyed the hell out of me when I was reading up on the game beforehand).  Masamune is a heavily-scarred victim of terrorism that hates terrorists to an incredibly strong degree, to the point where he is willing to cut them down mercilessly at a moment's notice.  

In Kurogane Kaikitan's world, Manhattan was destroyed by a mysterious explosion, obliterating the city and allowing Japan to sign a peace treaty with more of its political and military power intact.  As a result of Wall Street being gone and America's resulting economic downturn, Japan was able to take the helm of the world's economy, becoming a special financial zone and the battleground for various countries proxy terrorist activities.  This necessitated the creation of units devoted to dealing with this, which at first was the Special Police but more recently a militarized unit called SWAM.  The protagonist and his comrades are in training to join the Special Police.

The first thing most people will notice on beginning the game is the horrid use of Live 2d that can't be turned off.  I will say that it was a huge quality of life crapfest that they didn't allow the turning off of the sprite motion system, since it isn't that good.  Normally, I don't comment on visual aspects, but this was worthy of mention for its negative impact on the experience.

The prologue/common route of the game is pretty long, at just over seven hours on its own (though I wasn't reading it hurriedly, so I probably could have shortened the experience to five or six if I tried).  In exchange, the first two paths I did, Amakuni's and Kotetsu's, were roughly four hours in length each.   The prologue does an excellent job of developing the cast of characters to the point where you know which heroine you want to pick first (though you have to do Amakuni's or Fusehime's path first), as well as introducing the most important elements of the setting and setting the stage for the events that follow.

Amakuni

Amakuni is the protagonist's childhood friend, who was sickly as a child but became healthy by the time the story begins.  She is a master of combat iaido (the action of drawing the katana, slashing, then returning it to the sheath), and she is the classic 'self-proclaimed fiance' heroine.  Her path has a good mix of action, ichaicha, and feels, with two arcs (a 'buildup arc' and a finishing arc) that succeed in making her path feel like an extension of the prologue instead of being a random story based loosely on what happened before (as is common with a lot of VNs).  Her ending is highly emotional and somewhat bittersweet (a theme for this game as a whole).

Kotetsu

Kotetsu is a different animal entirely from the aggressive and tennenboke Amakuni, as she begins as a quiet loner who turns into a koakuma heroine later on.  I mostly picked her for my second heroine because I was extremely curious about her reactions to various events in the prologue and Amakuni's path.  She is the type of heroine who, once she falls for the protagonist, becomes somewhat emotionally dependent on him.  Her path is cute up until the point where events start rapidly occurring and certain facts about what was going on behind the scenes come to light.  Kotetsu's situation is one that draws pity naturally from the reader, so don't be surprised if you find yourself tearing up or wanting to look away because of some of the events of the story.  The ending is somewhat less satisfying than Amakuni's unfortunately, but that was perhaps inevitable considering the situation in both paths.

Nene

Nene is the teacher of the protagonist's class and the overseer/handler of the Kurogane unit for the First School.  Her path is significantly more twisty and labyrinthine than Kotetsu's or Amakuni's paths, whose trials were mostly personal for the characters involved.  Nene is that classic 'older heroine who falls apart in private' that Minato Soft and its subsidiaries love to put into their games.  She is also the equivalent of this game's Momoyo (in other words, the trump card/ultimate power that can flip the game board if put into play), albeit with none of Momoyo's whims.  I enjoyed this path, but like Kotetsu's path, the epilogue was somewhat unsatisfying.

Tamane

Tamane is the oldest member of the Kurogane unit, a member of a military family famous for its skills with the bayonet and rifle.  She often plays the mature and stern older sister role in the group, except that she, like Nene, tends to fall apart in private due to her weakness to those she cares for.  Her path, like Nene's, is pretty twisty and complex in comparison to the first two routes I played.  I enjoyed this path (the action toward the end, in particular) a lot, and the epilogue for this path is as good or better than Amakuni's, with the parting point in taste being whether you want sweet or bittersweet.  

Fusehime

I don't like Fusehime.

I have messed around with a lot of heroines I didn't like over the years, especially in serious games, but Fusehime is this game's Victim A, an out of place character who should have been just another class member.  I know that there is this temptation to put a morally naive party member into every 'group of friends', no matter how dark the setting, but Fusehime is particularly bad this way.  Naive, idealistic, and full of delusions about what her job is about... just about everything about her rubbed me wrong.  So, don't be surprised that I skipped this path, bwahahaha!

Kaikitan Path

This is the game's true path, devoid of romance.  It is also the path where a lot of the story's hidden elements come into the open and some of the best battles occur.  However, it is also a path that is somewhat rough emotionally on the reader if they came to like the main cast.  Honestly, I thought it was a bit too predictable compared to what it could have been with a little bit less teasing in the other routes.  

Extra Endings

All the heroines have extra path/endings after the Kaikitan path, based in a different timeline (specifically stated).  Like the original timeline, it is a 'what-if' world that is meant for those who like happy endings.  These secondary paths are actually reasonably enjoyable, but I honestly enjoyed the main game's paths more.

Conclusion

An enjoyable game based in a what-if world.  The world it is based in isn't the one of Majikoi, Tsujidou, and Tsuyokiss, for those who are curious.  It could have been a great deal better if they spent less time on SOL, but considering that this is Minato Soft (well, one of their subsidiaries), I suppose it was inevitable that it wouldn't be like that.  In a lot of ways, the version of Japan portrayed in the game reminds me of a Japanese-flavored America, in that it suffers from many of the same problems.