K'

To contrast the previous protagonist of the series, Kyo Kusanagi, K′ was made to be the "dark hero". The origins of both K′ and Maxima can be found in the Psikyo arcade game The Fallen Angels (Daraku Tenshi in Japan). This obscure 1998 release stars an emaciated goth in tight leather pants named Cool, along with a brawny, cybernetically enhanced police officer named Harry Ness. The end result is that K′ looks nearly identical to Cool. His namesake was taken from a clone character in the light novel, Blue Knight Beluzaga Monogatari, which is set in the same universe as the anime, Armored Trooper Votoms. During the early phases of development of The King of Fighters '99, K''s introduction to the 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. Eiji, a designer from the video games commented he thought that K' would be more popular than how he resulted and also noted K′ was too plain. Music composer Sha-V suggested that K' should yell "Dora!" or "Ora!" in order to make the equivalent to Kyo and Iori's shouts, "Doushita!" "Kurei!", respectively. Konny, another music composer, jokingly wonders if he is trying to say the word "dry" since the first word of his yell was "Dorei!".

Another K', a striker character from The King of Fighters 2000, was the final rendition of K' outside of a last-minute hairstyle change. He had brown hair and sported a violet costume. K′ has been noted by several of the series' designers as being one of the most difficult characters to illustrate since his look is very different when he is drawn by different illustrators. They also mentioned that the reason for his hair being bushier than need be may be a reflection of the conditions around him. KoF 99 was developed at the same time of Garou: Mark of the Wolves; developers noted several similarities between K' and Garou's main character, Rock Howard, which caused K''s designer to become very nervous.