神(かみ)のみぞ知(し)るセカイ(The World God Only Knows) is a series about a dating sim gamer who has been tasked by Hell to rid girls of escaped souls from Hell. If he doesn’t do his job then he gets decapitated! Despite how that sounds, the series is mostly comedic and has a more light-hearted tone.

The anime doesn’t adapt the entire manga. This is most obvious at the start of Megami-hen which skips forward from the end of KamiNomi2 to the Goddess arc in the manga.
Besides this, the anime ends at Megami-hen and doesn’t adapt the rest^A). This, interestingly, leads the anime to having a sad ending.
I’ll elaborate on this a little later.

Comparing the Anime to the Manga: the Manga has better comedic timing, if that even makes sense. Generally, the comedy in the Manga is handled far better - the framing, layout and such all aids it. The exception to this would likely be ‘I am your husband’s illegitimate daughter.’ where the Anime is superior.

The Manga has a bad and abrupt ending. I may elaborate further, but this is the short of it.

Hell has a bit of a problem. Occasionally, a spirit being tortured manages to escape. After escaping, these spirits hide in the gaps of people’s hearts, usually girls for whatever reason.
To reclaim the runaway spirits, Hell formed a team to capture them. This team then forms pairs of people (1 demon and 1 human) who have to the task of finding and capturing the spirits.
The human in the pair is tasked with filling the gap in the hearts of others, while the demon actually seals the spirit after it gets pushed out. Not all pairs work this way though.

The protagonist. He is an otaku (here we mean the more derogatory meaning of the term) obsessed with playing galge (“Gal Games” - “Dating Sims”). So obsessed in fact, that he has rejected reality. He is also insanely good at playing galge. So much, that he has earned the title of “Capturing God” - no girl can resist but falling in love with him.
Due to this, he is (involuntarily) recruited by hell to capture runaway spirits.
As time goes on, his rejection of reality slowly dies down more and more.‥ until he ends up falling in love with a girl himself.
He can best be described as intelligent, proud, shameless and efficient. He gets ridiculously good (er, perfect) grades in school and that’s only because he was under the impression teachers wouldn’t mind him playing games if he passed every test. His shamelessness is more in regards to him not caring about the fact people view him as a pathetic otaku… that and he can say and do things that would embarrass the hell out of any normal person.

The ‘younger sister’ of our protagonist.
She is a demon from hell, sent to be the ‘buddy’ of Katsuragi during his conquests.
She’s childish and a little flighty. She has an adorable obsession with fire trucks, which always brings an involuntary smile out of me.
Prior to joining the Runaway Spirits squad, she was a janitor. Because of that, she is very good at cleaning and is constantly carrying a broom around.
The manga comes up with a truly atrocious backstory for her, that almost single-handedly ruined the whole series for me. So basically, she’s the physical embodiment of an ancient weapon from hell.

Elsie’s friend from school.
Having graduated as an honour student, she goes down the typical path of ‘despite being great in school, I’m terrible at life’.
Something of a tsundere towards Katsuragi.

The review should have mentioned that the Manga’s ending is just bad. This section exists so that I elaborate on that.
That doesn’t mean right now.

I believe it would have been interesting if the conquest targets didn’t lose their memories after the conquest. I don’t necessarily mean that they literally remember everything but that they still have feelings left-over.
The series did, at some point, imply this was the case - although this turned out to be setup for Megami-hen.
This isn’t a flaw with the series; just something I thought would have been interesting.
The conquest targets having some memories left-over could have led to some more interesting situations - for example, Keima could have gotten their help in other conquests.

It should be noted that I do know the reason why this wasn’t present in the series…or, rather, I have a pretty good idea why. I’ll elaborate on that later.

• Official Anime Site
• The Wikia - Pretty bad, don’t bother.