Ken

Pictures from Toei Animations and information from Megchan's Digimon Sekai

The new enemy in the Digital World is not a Digimon, but a human boy! This boy calls himself the Digimon Kaizer and believes that it is his right to take over the Digital World and enslave all Digimon. His tools are the Black Digivice, the Evil Rings, and the Dark Towers. Using the Black Digivice he placed a lock on evolution so that no Digimon can evolve and thus they are powerless to oppose him. Then he captures them and puts Evil Rings around them, making them his slaves. The final step is to build a Dark Tower in each area. The Dark Towers amplify the power of the Black Digivice and Evil Rings, allowing the Kaizer to keep control of an area even when he's not there. Once the Dark Tower is destroyed in each area, the Digimon are free from his control and are able to evolve again, but only within that area. If they travel to another area where a Dark Tower still stands, they are just as powerless as before. The only way the new Digimon can evolve is by using their Digimental armor, which cannot be controlled by the Kaizer's Black Digivice. In episode 10, he invents the Evil Spiral which is more powerful than the Evil Rings. The Evil Rings could only control Champion or lower Digimon, but with the Evil Spiral he is able to control even Ultimate Digimon. Another advantage of the Evil Spiral is that it does not need the power of the Dark Tower and will continue to be effective even once the Towers are destroyed.

In the real world, the Digimon Kaizer is a boy named Ichijouji Ken. He's a genius, good at school, sports, everything. The DigiDestined first hear about him when he is being interviewed on TV after having won a computer programming contest. Little do they know the sweet, obedient boy they see on TV is actually the evil Digimon Kaizer! Ken thinks that because he's a genius, everyone else is beneath him and not worth his time. He even thinks this of his own parents. After episode 9, he leaves the real world in order to spend all his time in the Digital World. Although he has a partner Digimon, Wormmon, he never uses him in battle. Instead he uses his legions of enslaved Digimon to do his dirty work for him. Wormmon loves Ken, but Ken hates Wormmon, thinking he's not fit to be the partner Digimon of the great Digimon Kaizer.