The girl's deep brown hair, almost to the point where is could be mistaken for being black in colour, hangs down to where the white sleeves of her t-shirt ends; the rest of which, all the way from where the sleeves ended to her thin line of exposed midriff, is a blood red. Below, she wears a purple skirt down to her knees, gray tights running down into her shoes. Finally, she wears the digital watch-like D-Vice on her wrist; the gray dullness of its features broken only by a purple ring around its screen.
She first arrives in Book Six, intending to kill the tamer and Angels because of urges that her Demonhood causes her. She earlier murdered her own parents without remorse, just so she can go on her mission. In fact, the only being that she showed any kindness or compassion towards was DarkBiyomon. After meeting Rayleigh Thompson, she begins to doubt her original plan and develops a new one that involves pretending to be friends with the tamers. She does seem to actually enjoy being just another kid hanging out with her "friends," even joining in on a prank war (though that might have to do with her plan meant physically and emotionally hurting Kazu). DarkBiyomon held so much hope that Chiyo might change her mind and just be their friends.
Unfortunately, she remains firm about her decision. She used her power to cause all the girls to attack their boyfriends. Specifically, Rika went after Takato, Renamon went after Guilmon, Kari went after Davis (and pushing him out of a window in the process), Sora went after Tai, Yolei went after Ken, Mari and Jeri went after Ryder (Henry was trapped in the past, so Jeri attacked the boy since he was the only connection to her boyfriend and killing Ryder would end with Henry being dead too). When she arrived at the battleground, the tamers asked her to help. She pretended to try to use her ability on the girls, but nothing occurred. Ryder realized that she couldn't affect them because they were already under her control. She ended up shooting and killing Ryder herself. Unfortunately for her, she had used her power on Mari early on and thus her powers' effect on the tamer was less complete. Killing Ryder snapped Mari out of her trance and caused her partner to digivolve to her ultimate level and go on a rampage. Eventually, Chiyo managed to get in a position to kill Mari too, but Ryder revived from his "death" just in time to shoot the Demon. Though he was striving for just a wounding shot in her leg, he actually caused her a mortal wound. In the final moments of life, Chiyo seemed to regain her old personality that DarkBiyomon always knew was underneath her Demon personality.