Touken Ranbu

Touken Ranbu (刀剣乱舞 lit. Chaotic Sword Dance) is a 2015 Japanese video game developed by nitro+ and hosted on DMM (now EXNOA). It is a card-collecting and card-battle game in the same vein of Kantai Collection, except it's good-looking men who are collectible playable characters instead of women, and it's named Japanese swords belonging to Japanese historical figures that are the famous artifacts being personified into playable characters instead of ships.

Premise
Despite having a ton of characters, with new ones getting implemented on the regular, the game doesn't have an overarching plot. However, it does have a basic premise: in the year 2205, evil forces called the Temporal Retrograde Army (時間遡行軍 jikan sokōgun)/ Historical Revisionists (歴史修正主義者 rekishi shūsei shugisha) travel back in time to alter historical events. The player character, a faceless non-identity being called a saniwa (審神者) is appointed by the government to create an army of personified historical swords called touken danshi (刀剣男士 lit. sword men), run a Japanese-castle-like establishment called the Citadel (本丸, honmaru, lit. main circle (of a castle)) that serves as their housing and base of operations, and send the aforementioned sword men into battle to preserve history.

In Badfics
There are a number of common badfic tropes and conventions frequent in this continuum.


 * Given the above premise, it is simply all too easy, and far too distressingly common, to write the saniwa into a Sue who is more interested in being surrounded by charming men and being their object of reverence than fighting off the Retrograde Army and protecting history.
 * Creating sword OC is also observed, but not as common as saniwa OCs. Good OC swordsmiths will pay attention to several hard-and-fast rules about personified swords in this canon: that they are actual historical and/or legendary artifacts documented in Japanese history and that they're all male (they're touken danshi for a reason), and write OCs accordingly. Bad OC swords often make these mistakes:
 * Being a girl. This is often done by clueless writers who don't know what danshi means, or writers who know but purposefully ignore this rule, and almost always in order to invoke the Smurfette principle as a form of Speshulness. One wonders if these authors know there are at least two sword girl games where they can bring their OCs to instead.
 * Not being Japanese, not being a documented historical artifact, or both. This game is distinctly and strongly Japanese, unlike KanColle, and sword types classifications are not universal, making it highly unlikely that Excalibur will ever be a TouRabu character. Some authors go so far as to not care at all and create sword OCs entirely out of whole cloth with no basis in reality, thus missing the whole point of the game.
 * Not even being a sword. "Sword" OCs made from chain-sickles and iron fans have sadly been observed. These OCs' authors probably don't know that yari and naginata are canon characters by virtue of their blades' being forged exctly like sword blades and can be converted to swords, and thus considered nihontō.


 * Sword reproduction, either with a human Sue, with each other, or a sword Sue. Given that touken danshi are personifications born from inanimate artifacts, there are no known ways they can sexually reproduce another inanimate artifact to spawn a personification from, or create a being that is part-human, part-personification-of-an-inanimate-object. Much body horror implications ensue.