Kenji (ケンジ) is a character from Shin Megami Tensei IV.
Kenji joined the Counter-Demon Force to fight demons and protect Tokyo when he was eighteen, but sided with them once he learned they showed up to begin with thanks to God's scheme. He killed all the Angels when he was human in the past, but this made it impossible to open the Cocoon; the people cracked them open only to find everyone within dead. Kenji's partner from the Counter-Demon Force is said to have died in action while protecting him from demons, and it was this that made him realize the human body is weak and lead him to create Demonoids. Kenji also freed Ikebukuro of Xi Wangmu's control back when normal humans still lived in Tokyo. Back in the day he had to fend off any challengers who opposed his rule at Camp Ichigaya when he started the process of turning people into Neurishers or Demonoids, with the whole place becoming a war zone until he became victorious.
Kenji is the King of the alternate world Infernal Tokyo and received a prophecy from the White about intruders who would kill him should they obtain the remote to the Yamato Perpetual Reactor and has since sent his men out to hunt down the intruders. His base is in Camp Ichigaya and he resides in front of the Yamato Perpetual Reactor, where he stops the Samurai from retrieving the remote and says his title as King doesn't matter. He knows they are the intruders and says he is tired of killing and will only attack when Flynn says he wants the remote.
He mentions at the beginning of the fight that he has been fighting alone all this time and that he is fated to keep on fighting. As the fight progresses he starts laughing, saying the battle is turning him on and that he was afraid his lust for battle would awaken, asking if Flynn is also getting a thrill from the battle. As he takes more damage he attempts to ask that they stop fighting, saying he finally rebuilt Tokyo, however, his lust for battle and power overcome his reasoning. Taking even more damage, Kenji will state that he lost and fall to the ground, however this is a trap to get them to let their guard down. Having lost the fight, Kenji realizes the prophecy is true and asks the Samurai if they know what the Yamato Reactor really is and curses the White, dying afterwards.
In the DLC quest "Ancient One of the Sun", once the Ancient of Days makes it clear to Kiyoharu that he is here to exterminate humanity deemed unclean, a disheartened Kiyoharu will mutter that Kenji was right and he was wrong, meaning Kenji may have existed in Blasted Tokyo, however his fate is unknown (possibly dead due to Pluto's poison or God's Wrath).