Kazuya Mishima is a character in Bandai Namco's Tekken fighting game series, who first featured as the protagonist in the original 1994 game and later became one of the main villains of the series since becoming the penultimate antagonist of Tekken 2. He later returns as the main co-protagonist of Tekken 7, before assuming his role as the main antagonist again in Tekken 8. The son of worldwide conglomerate Mishima Zaibatsu CEO Heihachi Mishima, Kazuya seeks revenge against his father for throwing him off a cliff years earlier. Kazuya becomes corrupted in later games, seeking to obtain more power and later eventually comes into conflict with his son Jin Kazama. Kazuya Mishima possesses the Devil Gene, a demonic mutation, which he inherited from his late mother, Kazumi Mishima, which can transform him into a demonic version of himself known as Devil Kazuya . Devil Kazuya has often appeared as a separate character in previous installments prior to becoming part of Kazuya's moveset in Tekken Tag Tournament 2 and later games. Kazuya Mishima is also present in related series media and other games.

Heihachi Mishima is a character in Tekken fighting game series created by Bandai Namco Entertainment, serving as its main antagonist. Introduced as the boss character from the first Tekken video game from 1994, Heihachi appears as the CEO/leader of a military firm known as the Mishima Zaibatsu founded by his father Jinpachi Mishima. Heihachi was the protagonist of Tekken 2 and one of the two main characters of Tekken 7 along with his son Kazuya Mishima, furthermore Heihachi was a boss character in two additional main installments of the series. He is opposed by many of his relatives who wish for his death out of revenge and to take over the Mishima Zaibatsu. This happens across the series and one of the creators of Tekken Katsuhiro Harada has called it a "family feud". Heihachi wants to defeat his son and grandson, Kazuya Mishima and Jin Kazama respectively. Heihachi's backstory and motives are revealed in Tekken 7, in which he is killed by Kazuya and thus does not appear in Tekken 8. Heihachi has two known illegitimate children who are playable in the series, the first is the hero Lars Alexandersson, who debuted in Tekken 6; and the second is Reina, who was introduced in Tekken 8, uses some of his moves and has a similar personality, and is later revealed to be also a Devil Gene user as both Kazuya and Jin.