Originally developed as an ersatz Guilty Gear due to the original license being owned by Sammy, the BlazBlue franchise has grown into its own universe with everything from the original fighting games to light novels and even an anime adaptation set to appear with most of the same voice cast from the game.
Many years ago, a large being appeared known only as "The Black Beast." It ravaged the entire world, leaving destruction in its wake. All conventional weapons were useless against it, and even nuclear bombs proved to be useless against this strange new threat. But one day, a legendary band of warriors known collectively as "The Six Heroes," wielding magic and special weaponry, rose to fight the Black Beast and bring peace to what was left of humanity.
In the aftermath, the Novus Orbis Librarium ("The Library" or the NOL) united most of humanity under a single government, and organized the construction of "Hierarchical Cities" at high elevations. The death of the Black Beast covered most of the world in "seithr," a magical energy that could be used to power magic and technology, but at the same time too much exposure could cause living things to go insane or even die, so these cities were built at high elevations, on mountains, and similar formations.
There was a relative period of peace, but soon a faction emerged that sought independence from the rule of the Library. The Federation led by the city of Ikaruga ended up fighting in a civil war with the Library, but the city was mercilessly wiped out by NOL forces, and the survivors scattered to the other cities.
Now in the present, in the 13th Hierarchical City of Kagutsuchi, a notorious SS-class criminal known as "Ragna the Bloodedge" has reportedly set his sights on destroying the main NOL branch there, just as he has in other cities around the world. This has sparked bounty hunters and soldiers of all kinds to flock to the city. Some seek the massive bounty his capture would bring, others seek the "Azure Grimoire" (or BlazBlue) that Ragna supposedly holds, an artifact that contains immense magical power to anyone who wields it, and still others have their own reasons for coming to the city.
Noel Vermillion has been revealed as the true holder of the Azure Grimoire, but Hazama appeared at the last moment to steal it from her. While Ragna and Jin nurse their respective wounds, the major players suddenly take an interest in Noel as Hazama seeks to turn her back into Mu-12. Meanwhile, Rachel is having issues dealing with a highly advanced AI that has been resetting the flow of time over and over, Tsubaki is wrestling with her duty to the Imperator over being ordered to kill her dear friends Noel and Jin, Hakumen is being kept prisoner and Kokonoe prepares her contingency plan should things go wrong.
BlazBlue: Calamity Trigger
The game that started it all. Only ten characters were playable in this version, including the final boss character v-13 (pronounced "Nyu," as in the 13th Greek letter).
BlazBlue: Continuum Shift
This game continued off the story from the first game and added two new playable characters to the mix: Tsubaki Yayoi and Hazama. A third, Mu-12, could be unlocked after beating the Story mode. Also, the burst and guard systems were tweaked a bit.
BlazBlue: Continuum Shift II
Technically a patch for the previous game (and was a downloadable patch for the console versions) but released as a brand new title on the PSP and Nintendo 3DS. This version also introduced three more playable characters that could be downloaded for a price or patched in for free to play against online: Makoto Nanaya, Valkenhayn R. Hellsing, and Platinum the Trinity.
BlazBlue: Continuum Shift Extend
This one contained all previous playable characters for no extra charge and added one more: Relius Clover. Technically another expansion pack and patch to BB:CS, but released as its own retail copy instead with a couple new modes attached: Unlimited Mars mode, forcing the player to fight a string of Unlimited-powered AI opponents with no continues, and Abyss mode which added RPG elements to the normal fighting game as the player took one character down a set number of levels depending on selected difficulty.
In addition, the story mode included paths for the new characters not mentioned in the original Continuum Shift, and offered a truncated story of Calamity Trigger with new cutscenes animated by Nitroplus.
BlazBlue: Chrono Phantasma
A true sequel to the events of Continuum Shift. This game was released only for the PS3 and PS Vita, as Mori claimed that the size limitations of XBOX 360 discs made it difficult to release the game for that system without removing some content.
Chrono Phantasma included seven new playable characters, including two who would later be added as DLC: Yuuki Terumi (the original version of Hazama) and Kokonoe. Gameplay-wise, the guard-break system was completely overhauled from Continuum Shift and a new system called "Overdrive" was introduced, allowing a character to sacrifice a burst each round in order to briefly extend combos or make their Distortion Drives even stronger, which could result in an "Overdrive Finish" if the enemy was successfully KO'd with one.
Rather than focus on each character's story individually as done in previous games, the story mode largely split into three sections: Chronophantasma, Six Heroes, and Sector Seven. The three branches would later unite into one path for the True Ending of the story, which brought the protagonists together to fight a rampaging Take-Mikazuchi called down by the Imperator herself.
The game also introduced fake arcade lobbies online, which allowed players to meet up in giant rooms where they could challenge one-another by having their avatar sit at a machine across from the player they wished to play, simulating a local arcade experience. Some lobbies offered special prizes for avatars or flags.
BlazBlue: Chrono Phantasma Extend
An expansion of the previous game expected to be released in the summer of 2015. This game will include a playable Celica A. Mercury as she largely relies on a copy of Nirvana (Carl's Nox Nyctores) created by Kokonoe to fight for her. The game also includes extra story content that was only found in the spinoff manga Remix Heart.
BlayzBloo: Super Melee Brawlers Battle Royale
A multiplayer party game released after Calamity Trigger, using super-deformed main cast characters. BlazBlue: Clone Phantasma would be released a few years later, another party game with more content.
Visual Novels set in the BlazBlue universe, though 150 years before any of the events from the main games happened. The first game, Code: Embryo, involves high school student Toya Kagari stumbling onto a mysterious girl named "Es" from the Mitsurugi Agency, and from there being dragged into experiments invovling Seithr, Distortion Drives and more.
The sequel, Lost: Memories, sees the return of the two main characters from the previous game, as well as a few more adventure elements sprinkled in to the game.
A Japan-only mobile-based card game
There are three different manga stories created in the universe.
A retelling of the Calamity Trigger story in 8 chapters.
Another telling of the Calamity Trigger story, but from different perspectives.
A BlazBlue story set in and around the NOL Academy, with a new protagonist named Mai who was transformed into a girl for reasons unknown.
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BlazBlue: Alter Memory, a 12-episode anime series which retold the stories of the first two games along with some added fanservice, bringing many of the original VAs for each character in the games to voice their animated counterparts.