Kusanagi Saisyu is a character who debuted in The King of Fighters '94 as a victim in Rugal's gallery of defeated fighters. He appears as a mid-boss in The King of Fighters '95 and becomes a regular character for the first time in The King of Fighters '98. He was originally meant to have died in KOF '94, but was added in at the last minute of developing stages for KOF '95.

Introduced in The King of Fighters '94, Saisyu Kusanagi (Kyo Kusanagi's father) is the current patriarch of the Kusanagi bloodline and master of the sacred flame. Unlike his son, he dons an old fashioned style Kusanagi clan outfit and utilizes more basic traditional martial arts techniques. In 1994, Saisyu embarked on a quest to challenge fighters from around the world. Kyo and his teammates (Benimaru Nikaido and Goro Daimon) learn of his demise just before the final match in KOF '94. Saisyu apparently challenged Rugal Bernstein and is beaten badly, it is implied that he allegedly later succumbed to the injuries he sustained before the finals.

However in The King of Fighters '95 it is eventually revealed that Kusanagi survived, was then brainwashed by Rugal's secretary Vice in order to compete as a mid-boss in the semi-final round. He is supposedly defeated by his son Kyo and his teammates. Upon his second defeat, Saisyu goes in to self-exile.

(Source: SNK Wiki)