The voice of Yuki, Kyo's girlfriend, can only be heard as a very brief line heard in the 3 Heavenly Vessels Team ending (consists of Kyo, Iori, and Chizuru). Tomoko Kojima won the part in a contest that SNK held during the game's production.
In order to decide who would become the members of the '97 Special Team, three polls were conducted by the video game journals Weekly Famitsu, Gamest and Neo Geo Freak, in which readers voted who was the character they wanted to see in the team. The Neo Geo Freak's winner was Billy Kane and Famitsu's winner was Ryuji Yamazaki. Blue Mary was first in the Gamest poll, barely beating Duck King from the Fatal Fury series who was second in the poll via a few mere votes. Additionally, the three journals created a team, which players can view an image of them after beating the game in the Japanese version. The special team created by the Neo Geo Freak's staff was a team of fire wielders: Billy, Kyo Kusanagi, and Mai Shiranui. The Gamest's team created was composed of Terry Bogard, Blue Mary and Joe Higashi, while Famitsu created a team composed of Chang Koehan, Choi Bounge and Ryuji Yamazaki.
Although Blue Mary already had two designs in the Fatal Fury series at this point (her original debut design and her Real Bout Special design), her designer wanted to use her Fatal Fury 3 (1995) design as he liked it more.
In order to have all of the eight servants from Orochi confirmed by this game, Ryuji Yamazaki was chosen to be the new member as the staff noted him to go from being a villain to an antihero and liked that he was similar to a snake (as the ancient Orochi was a giant snake).
In order to adapt him to KOF, the game planner had to provide new moves to Ryuji Yamazaki. The new moves were initially noted to be failures, but designers later thought of them as successful.