Shiharu Genesis

Long ago, the cherubim Lucifer turned his back to God and waged war with His angels...
...but in the end, he was slain and his army scattered to the winds.
Six thousand years later, Lucifer has been reincarnated in the body of a young child... and it's only a matter of time before those memories of the past war awaken and the world is once again thrown into chaos.
Anticipating this, a single angel volunteered to be sent down to prevent the resurrection before Lucifer's minions find their leader...
...thing is, Lucifer reincarnated as a sweet, ditzy little girl, who wouldn't hurt a fly.