Violence / Gore: The violence is mostly of the comedic variety. Characters fall into things, get punched and one gets shocked with a "perfectly safe stun gun".

Nudity / Sexual Content: I counted exactly 3 instances of strategically covered nudity. At one point Elsie unexpectedly joins Keima in the bath, the lights are off so initially he doesn't realise she's there but when he does, he immediately gets out and covers up. Elsie is covered by her magic shawl like a bikini or short top.
When two people are discussing another character, nudity is used to show her vulnerability in contrast to her outwardly "standoffish" attitude. Keima's mother is show in the bath.

Theological themes: It's all there in the premise of the show. The lost souls look kind of like ghosts and Elsie refers to Keima as "Divine One".

Negative themes: Some minor swearing.