Killy 's first encounter with Cibo is in the lower levels of the Corporation in The Capitol, where she has been imprisoned for attempting to access the Net Sphere with an artificially created version of Net Terminal Genes. Her failed attempt to access the Net Sphere led to the appearance of the Safeguard, which destroyed the entire lab facility that Cibo was conducting the experiment in. The death and destruction resulting from Cibo's failed experiment led the governing body of the Corporation to convict and imprison her.
Cibo's first form is the decaying upper torso of a woman kept alive by machinery inserted into her body. She convinces Killy to take her with him by stating that he needs her hacking skills to access the files he is looking for. Afterwards, she transfers herself to a replacement body and aids Killy in destroying the Corporation's President. Following that, Cibo leaves the Corporation to travel with Killy.
She has a subtle connection with the Netsphere, but even if she were able to make a direct connection to it, the Safeguard would be invoked immediately.
Later in the manga, Cibo's physical body is killed by the Safeguard, but her mind takes over Sanakan's body. However, Sanakan's consciousness still remains in the body, forcing the two women to share it. Cibo is able to suppress Sanakan's mind, preventing it from gaining control, although on several occasions the Safeguard managed to take over.
After the encounter with the Silicon Life, Mensab and Seu, Killy is teleported to an alternate reality, where he meets Cibo in her old form. Both versions of Cibo face one another and wish to return to the original reality. During the attempt, the alternate Cibo is killed by a Silicon Life creature, while the original Cibo is severely damaged and Sanakan's mind uses the opportunity to resurface. When Sanakan discards away Cibo's genetic information (or mind), it is absorbed by the dead body of the Cibo from the alternate reality, leading to her revival in that body.
After Sanakan's transfer to the Governing Agency, a Level 9 Safeguard (the highest level) illegally downloads itself onto Cibo, resulting in her ultimate transformation into the Level 9 Safeguard and the newly-bred Net Terminal Gene. The sphere that she stores in her lower abdomen carries the gene that can save the city if it's taken to its very edge. Cibo is heavily weakened by Killy's GBE shortly after her transformation, reverting to a childlike state and eventually falling into the hands of the Silicon Creatures despite Sanakan's efforts to find and protect her. Sanakan asks for a return to the Base Reality, which is her final time there. She tears through Silicon Creatures to reach Cibo, and then encounters a First Class Exterminator. Killy destroys the Exterminator and recovers the orb, though the Exterminator destroys Cibo and Sanakan during the battle.
At the end of story, Cibo's mind is shown to have survived in a backup storage device. She has been transferred to a temporary storage area removed from the Base Reality, with only partial memories of Killy and her own past.