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.