Residual Information

Residual Information (残留情報) refers to traces of information left behind in objects and surroundings by events and phenomena which occurred in their vicinity in the past. There are numerous causes of residual information and methods of use and elimination, on both Magic and Science Sides.

Magic
In Rosenthal-style Necromancy, the residual thoughts of the deceased are used as a key code in order to slip an artificial soul into the corpse, and can take shape outside of the body, assuming a dangerous form if not properly controlled.

Necromancer Arc
When Esther Rosenthal was inserting Huotou into Hitokawa Hasami's body, the residual thoughts in the corpse took the form of a floating brain. When Accelerator touched it, Hitokawa's memories flooded into his mind.