SNK's The King of Fighters series includes a wide cast of characters, some of which are taken from other SNK games. The fighting game takes place in a fictional universe in which an annual series of 3-on-3 or 4-on-4 fighting tournaments are held.

The first game in the KOF series introduces the initial protagonist, Kyo Kusanagi, a young Japanese fighter with pyrokinetic abilities who is the heir to a powerful group of martial artists. Kyo fights against the Kusanagi clan's enemies, his rival Iori Yagami, and the snake entity Orochi and its human followers, among others. The first four games in the series revolve about these fights, while The King of Fighters '99 introduces a second story arc, revolving around K', a young man who seeks to destroy the mysterious NESTS organization because they kidnapped him at an early age and stripped him of his past memories so they could force him into a fighter under their control. A third story arc focuses on Ash Crimson, a mysterious fighter with green flames who steals the powers of the clans that sealed Orochi in the past for unknown reasons. A mysterious group of villains, Those from the Past, also wants to obtain Orochi's power for the purpose of giving it to their unknown master. A fourth story arc currently involves Shun'ei, a young Chinese fighter who possesses unknown supernatural powers, as a result of being connected with Ash's time-traveling paradox.

The plot and the characters came from the Yamata no Orochi legend. There are also several characters in the games that are parodies or homages. Merchandise based on the characters has also been released, including action figures and keychains. The characters have garnered praise from several video game publications for the quality of their designs and movesets. Comments focused on the lack of improvements in some of the characters, but added that the roster is greatly diverse.

Cast creation and influences

The developers of the series claim that their prototype version for King of Fighters was going to be a Double Dragon-style side-scrolling beat 'em up titled Survivor. It would have used only core characters from the Art of Fighting and Fatal Fury series, specifically allowing players to play Robert Garcia and Terry Bogard for location testing. However, the idea was quickly abandoned. Since the developers were attached to the idea of the two series cross-over, they eventually agreed to make their idea into a fighting game. Characters from the Ikari Warriors and Psycho Soldier games were also added in the spirit of other gaming genres considered for their final product. The concept of a three-man team was one of the ideas kept from the side-scrolling version. Flagship director Toyohisa Tanabe asserts that the Art of Fighting and Fatal Fury fighters were added specifically for adults. The newer King of Fighters characters were aimed to appeal to younger and newer audiences. He adds that every original character for the series was added based on the developers' strong desire to make one. For example, he agreed to include characters such as Benimaru Nikaido and Chang Koehan to add an off-beat variety to the cast, which he had previously deemed to be too serious. Later in the series, their approach to creating their characters altered slightly, to also serve as a type of fan service, which he refers to as a collaborative effort between fans and the staff.

Several characters that appear in the series are parodies or homages to either anime, manga, actors, films or television shows that held the creators' interest. Noticeable examples are K9999 and Zero. Several characters were added to the roster by Eolith's desire when this company sponsored SNK to attract fans from Eolith's region.

When designing characters for the first KOF game, developers wanted a new, "snazzy" hero who would easily fight against Fatal Fury and Art of Fighting characters. Initially, this character was called Syo Kirishima, but late in the production, his name was changed to Kyo Kusanagi. This was done in order to relate him with the Yamata no Orochi legend, which was used as an inspiration for the first story arc (and specifically featured a majestic sword known as Kusanagi no Tsurugi). To continue with the idea of the Orochi plot, the designers gave several other characters, such as Kyo's rival Iori Yagami, who has similar characteristics to Kyo. In The King of Fighters '99, to contrast the previous protagonist, K' was made to be the "dark hero". The introduction of K' to the KOF series was meant to remove popular characters Kyo Kusanagi and Iori Yagami from the roster, though this idea was scrapped in the game's release. Due to the large additions of teenage characters in the series, SNK decided to add several middle-age ones to balance them.

Yasuyuki Oda said while researching for the game's new characters, they avoided stereotypes like Japanese sumo wrestlers to produce more diversity in the cast which includes characters of various nationalities. Oda coined the term "Kyo-ify" based on the series' main character Kyo Kusanagi in regards to the stylishness presented in the cast. As a result, Oda wanted the fighters to look as appealing as Kyo. Art director Nobuyuki Kuroki found it unfair that only a few designers were included on the staff. Eisuke Ogura created newcomers Shun'ei and Sylvie, distancing them from previous veterans. Kuroki regarded Shun'ei as important to the narrative, desiring his personality to contrast previous leads. Main characters Kyo Kusanagi and Iori Yagami underwent a major redesign to fit the series' new story arc while at the same time the development team tried to keep their appeal intact. Kuroki said he made this move despite fearing a negative response based on the rivals' popularity.

Introduced in The King of Fighters '94

Kyo Kusanagi

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is a high school student whose family possesses an ancient set of pyrokinetic abilities. Kyo is the leader of Japan Team and one of the three Sacred Treasures.

Benimaru Nikaido

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is a model who fights with shootboxing and has electrokinetic abilities.

Goro Daimon

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is a former gold medalist in Judo and a mentor to his own dojo. After KOF '97, Daimon retires from being a fighter and returns to the Judo circuit representing Japan.

Chin Gentsai

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Chin Gentsai is an elderly fighter who uses various styles of Kung Fu and fights primarily with drunken boxing. An original member of the Psycho Soldier Team, Chin is Athena and Kensou's master and also a mentor to Bao and Momoko.

Chang Koehan

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Chang Koehan is a giant criminal who fights with a large metal ball attached to a chain. He is also a member of Kim Kaphwan's team alongside Choi.

Choi Bounge

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Choi Bounge is a small criminal who fights with Freddy Krueger-esque claws. He is also a member of Kim Kaphwan's team alongside Chang.

Heavy D!

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Heavy D! is a professional boxer who was banned from regular competition after severely injuring his opponent. While introduced in The King of Fighters '94, he only returns in The King of Fighters '98.

Lucky Glauber

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Lucky Glauber is a former professional basketball player and a Karate champion with a penchant for street fighting. While introduced in The King of Fighters '94, he only returns in The King of Fighters '98.

Brian Battler

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Brian Battler is an American football player who also makes use of wrestling. While introduced in The King of Fighters '94, he only returns in The King of Fighters '98.

Rugal Bernstein

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Rugal Bernstein is an arms dealer and the organizer of The King of Fighters tournament. Capable of copying any technique after seeing it performed once, he makes heavy use of Geese Howard's Reppuuken and Wolfgang Krauser's Kaiser Wave ki-attacks. Rugal also has techniques of his own, such as a slashing kick called Genocide Cutter. In KOF '95, he appears in his superpowered form. His regular form can be selected in KOF '98 and its Ultimate Match remake. Omega Rugal returns in KOF 2002 and its Unlimited Match remake as well as in KOF XV.

Introduced in The King of Fighters '95

Iori Yagami

Iori Yagami is a descendant of Yasakani, gifting him blue flames that he uses to fight. However, the curse of the Orochi gives him a berserker form in KOF '97 called Orochi Iori which appears as a boss. Iori also often appears as Kyo's rivals not because of their clans' past but because of a personal grudge.

Saisyu Kusanagi

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debuted in The King of Fighters '94 as a victim in Rugal's gallery of defeated fighters. He appears as a sub-boss in The King of Fighters '95, and becomes playable for the first time on the screen in The King of Fighters '98, although he was selectable in the console versions of The King of Fighters '95 as a secret character. He was originally meant to have died in The King of Fighters '94, but was added in at the last minute of development for The King of Fighters '95.

Saisyu Kusanagi is the previous head of the Kusanagi clan, who left his family to face worthy opponents across the globe. After his defeat by Rugal, he is brainwashed by his secretary Vice to fight his son, Kyo. Upon his defeat, he regains his senses and escapes from Rugal's missile silo base. Although Saisyu is missing, in The King of Fighters 2001, he appears before Shingo Yabuki and spends a year properly teaching him the Kusanagi fighting style. He is still playable in The King of Fighters '98 and Neowave. He returns in the story during the prologue from The King of Fighters XIV asking Kyo to meet Tung Fu Rue in the upcoming competition. In the 2010 live-action film adaptation of The King of Fighters, Saisyu is played by Japanese actor Hiro Kanagawa.

Introduced in The King of Fighters '96

Leona Heidern

, Heidern's adopted daughter introduced in The King of Fighters '96, replaces him as he takes on a more active role behind the scenes, investigating occurrences parallel to the tournament. Although she tends to be very quiet, Leona was conceived to be an Orochi descendant at the time of her debut, and her designers took special care to let their interests at the time reflect in her actions. Her official nickname is The Silent Soldier. Although she recovers from her childhood trauma at the end of King of Fighters '97, she leaves the team after attacking her friends in the Riot of the Blood state at the conclusion of King of Fighters 2003 and tries to regain her focus from within her personal time.

Vice and Mature

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and appear as members of Iori's Team in The King of Fighters '96. The designers at the time created both Vice and Mature with the image of a "cruel woman" and a "ruthless woman", respectively. Their origin story is mostly based on the notion of Rugal employing secretaries prior to The King of Fighters '96. Both women were unavailable during location testing and were likely finished near the end of the game's production schedule. Aside from serving Rugal, both women were also spies and wielders of Orochi. They form a team with Iori in order to keep an eye on him, but both of them are killed by Iori.

Since then, both have appeared in the "dream match" games The King of Fighters '98 and The King of Fighters 2002 (games in the King of Fighters series with no canonical connection). Vice has also appeared in Capcom vs. SNK: Millennium Fight 2000 and the sequel. Mature is a playable character in The King of Fighters XII, exclusive to the home console version of game.

With Vice's return in The King of Fighters XIII, Iori's 1996 team is reunited for the first time since The King of Fighters 2002. In The King of Fighters XIII, both women are spirits, reflecting their fates at the end of the 1996 tournament. With the rise of a new Orochi crisis brought on by Ash Crimson's meddling, they convince Iori to enter the new tournament to settle matters and stop whatever it is Ash has in mind.

The duo returns in The King of Fighters XIV to team up with Iori once more since The King of Fighters XIII. After witnessing the possible return of Orochi, they quietly return to the shadows from once they came.

In The King of Fighters XV, the two are briefly mentioned in Iori's background story telling him that they would stand back and watch him from the audience this time. They are set to return as downloadable content.

In the 2010 live-action film adaptation of The King of Fighters, Vice is played by Bernice Liu, and Mature by Monique Ganderton.

Chizuru Kagura

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