
The story takes place two years after the events of the 1997 King of Fighters tournament and the defeat of the evil being Orochi (with the two responsible, Kyo Kusanagi and Iori Yagami, missing-in-action). The "Command Mode" system was also removed (with the game being based on Advanced Mode), and the "MAX Mode" system was revamped into two separate power-up states: the offensive "Counter Mode" and the defensive "Armor Mode". The sixth installment of the King of Fighters series (and the sequel to The King of Fighters '98: The Slugfest), King of Fighters '99 brings a darker sci-fi aesthetic to the series while introducing the "Striker" system: a gameplay mechanic where players choose an additional teammate for use in dedicated assist attacks.

It was subsequently released for the Neo Geo AES and Neo Geo CD later that year, and is the last game released for the Neo Geo CD.

The King of Fighters '99: Millennium Battle is a 2D tag-team fighting game developed and released by SNK for arcades (running Neo Geo MVS hardware) on July 22, 1999.
