Ego (エゴ*)? is a demon in the series.
In spirituality ego is described as an illusion in nondualism, mysticism, and meditation. The "sense of doership" is the part of the individual existence that believes it is a human being. It believes it must fight for its existence and is unaware of its true nature. Ego is associated with the mind and time, where it believes it must think in order to prove its existence rather than knowing its own self in the present.
Devil Children Black Book & Red BookEdit
Ego ranks up to Satan.
Devil Children Black/Red/White BookEdit