When he was young, Ken and his older brother, Sam, found a digi-vice. Later, Sam died after being hit by a car (which we see as a flashback in Episode 21: "The Crest Of Kindness"). Some time after that, Ken felt guilty, as he wished he would never see his brother again. Then an e-mail from a mysterious figure told him to use the digivice to escape the guilt. Ken did, and was transported to the dark ocean. His digivice turned dark and Ken adopted several aspects of Sam. Since then he became a boy genius, good at everything that was wither sport or intellect related. But in the Digital World, Ken took on the guise of the evil Digimon Emperor and used his Black Rings, Control Spires, and Dark Spirals to take over. He fought the digi-destined until he created Kimeramon. The fight that followed resulted with Wormmon's death. With the memory of Sam's death back to haunt him, Ken went through some soul-searching. When Wormmon was reborn, Ken sees the error of his ways and intends to redeem himself. It took the gang time to trust him, but Ken was eventually welcomed with open arms. Eventually, it turned out Ken came to the Digital World long ago with a boy named Ryou Akiyama. They were fighting a evil Digimon named Milleniumon, whose death scattered his data in the form of Dark Spores, one of which entered Ken's neck. It was the source of Ken's subconscious desire to be like his brother, and the reason Oikawa used him. In episode 50 of the second season, it is revealed that twenty-five years after the battle against MaloMyotismon, Ken became a private investigator and married Yolei. They have three children.