The Eminence in Shadow of the Strongest Six Year Old Sage

Story:

"Looks like I defeated the Demon King" The man who was once the strongest sage is reincarnated as a 6-year-old boy Eddie. Eddie, who inherited the memory and magical power of a past life and received more power than in the previous life, decided that … "I want to live like a boy!" I want to spend mediocre and calm days in this life! But is it? By day, is he a nice little boy of six, and by night, is he a great ruler of darkness?