During the events of DEM, System X malfunctioned by a Manifest-created virus, in an attempt to destroy him. The only thing that could save him, System C, was obtained by Lindsay and Yellow, and X was recovered. To thank the two, X warned the Cutting Crew about Katherine Steel and gave Lindsay and Yellow a daughter, since Lindsay was half-animatronic. The souls of Lindsay and Yellow accelerated Lucile's growth, and she aged from 6 to 15 in a matter of months. When her mother was thrown into a Manifest-turing chamber and infected, Lucy went into depression, eventually getting the courage to serve as a general in the CC Militia, under training of Spanish Marcher and Seven. When her mother died, she stepped down, to take out SFP herself.
Lucy seems shy around new animatronics, and is afraid of not being able to live up to her mother's name. But, she is very brave and optimistic, and when her mother was turned into a Manifestian, Lucy went mad with determination to kill all Manifest soldiers.