Yuji Kiba

History
Originally human, Kiba became a natural Orphnoch after dying within two years when he was in a coma as a result of horrific car crash which killed his parents. Once revived, overwhelmed by is heighten senses, Kiba was astonished from learning his parents' death to overhearing that his uncle forsaken him and sold his family's company. Though it got worse when Kiba learns that his girlfriend Chie Morishita left him for his cousin Kazuaki. Killing Kazuki in a maddened rage, Kiba attempted to commit suicide but finds himself in a Smart Brain owned mansion and meeting Smart Lady, explaining his current status. When he is called by Chie later, he is heartbroken when she names him the culprit in Kazuaki's murder, outrunning the police before he murders Chie out of scorn.

After finding Yuka, another naturally born Orphoch, Kiba meets Smart Brain's CEO Eiichi Toda, who reveals more information of the Orphnochs and Smart Brain's goal to make their kind the dominant species and eradicate those who can not become Orphnochs like them. After hearing the genocidal intent, witnessing Naoya being made an Orphnoch, Kiba quickly comes to deplore the organization's tactics and resolved to protect humans and fight Smart Brain after Kyoji Murakami becomes the new CEO. However, Kiba becomes a rival of Kamen Rider Faiz, fighting him every time they encountered one another until they learned each others' true identity and intent as they joined forces. He once uses Takumi's Faiz Gear to fight as Faiz.

Television Ending
After he believed Yuka to have been killed by the police, Kiba turns against his ideals and eventually replaces Murakami as the chairman of Smart Brain. After acquiring the Kaixa Gear, Kiba eventually fought Takumi as Kamen Rider Kaixa before his faith in humanity is restored. In the end, Kiba was mortally wounded by the Arch Orphnoch, grabbing the monster to allow Faiz to kill them both, though only the Arch Orphnoch barely survived.

Movie Ending
In the film Kamen Rider Faiz: Paradise Lost, taking place in a world mostly dominated by the Orphnochs, Kiba becomes the primary user of the Orga Gear after being tricked into thinking that he, Yuki, and Naoya are sent on a suicide mission. As Kamen Rider Orga, Kiba battles Faiz in a fighting transitioning from Kamen Rider to Orphnoch. In the end, after Takumi finally gets through to him, Kiba sacrifices himself to hold off the Elasmotherium Orphnoch so Faiz can destroy it. In his final moments, Kiba has Takumi promise to fulfill his dream of peace between the humans and the Orphnochs.