Kazuya Mishima operates as a foundational yet primarily unseen force within the depicted events. He is the son of Heihachi Mishima and the father of Jin Kazama. His very existence fuels the central conflict, specifically concerning the hereditary Devil Gene—a genetic anomaly granting superhuman strength and demonic transformations—which he transmitted to Jin.

Multiple flashbacks detail Kazuya's tumultuous history with Heihachi, climaxing in Heihachi killing him during the second King of Iron Fist Tournament's final battle. This execution arose from Heihachi's objective to eradicate all bearers of the Devil Gene. Kazuya's demonic abilities, unleashed through this gene, presented a critical threat that Heihachi aimed to eliminate.

Though Kazuya appears physically only in these flashbacks, his legacy profoundly shapes pivotal characters. Jin wrestles with his dual heritage, trained defensively in the Kazama style by his mother Jun yet conscious of the aggressive Mishima techniques originating from Kazuya. Heihachi manipulates this lineage, instructing Jin in Mishima combat while covertly planning to incite and annihilate Jin's inherited Devil Gene.

Kazuya's reported death and the exposure of his demonic power cement the enduring Mishima conflict. This positions him as the catalyst for the tournament's unfolding events and Jin's internal battle against his own potential transformation.