Demon cells (鬼の細胞 Oni no saibō) are mysterious cells discovered in the East. These cells stimulate the functions of the living beings, but their effect is too strong, and people, who receive portion of these cells, usually die. The cells themselves are withdrawn from demons. Kokonoe Mercury has these cells under her study, but details are unknown.
After the Event Weapon Dispossession Operation, a mortally wounded human was taken to Kokonoe's lab and injected with the cells in order to preserve his life and provide adequate data for Kokonoe's research. Thanks to combining the cells with a replica of Nirvana's core, his life is spared.
The cells also had an effect on his appearance, as his skin changed to a deep crimson red, he had a mass increase in weight and height, and gained phenomenal strength. Some of his limb were replaced by machinery.
Since then, this human is known as TR-0009 Tager.
Hakumen notes that the act of a scientist injecting the cells into a living being can only raise questions on a scientist's moral beliefs.