Eldritch Little Shit

One day, an honor-student younger sister who supports her NEET older brother gets caught up in a sketchy black magic ritual—and has her body hijacked by the Evil God, Azathoth-Urara. Urara tries to wield its divine authority to put humanity in its place, but in a little sisters body, its power is basically "so weak~♡." An obnoxious cohabitation life begins whether they like it or not with Urara, who has turned into an insufferably useless brat putting on airs...! An indescribably vulgar comedy that makes you want to "correct" this brat the moment you read it!!

Source: Kodansha, translated