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 Neurisher