I heard that it was made by Torinone. Can someone confirm that?

I found it in his twitpic, along with some initial skteches. So, yeah. Probably.

Wasn't sure if edits warranted an artist tag.

I don't mean to start any arguments, but I find it very doubtful that torinone drew this. The style is soo different from his usual stuff, and this looks like official art.

Well... it says Yu Aoki in the info up in the corner, which I assume means Ume Aoki, who designed all the characters (and created Hidimari Sketch, for that matter) and did other artwork for the series. This is either 100% official Aoki work that Torinone just happened to post, having gotten the sketches and such elsewhere, or she sat down to reproduce the official art and we are looking at the best style parody I've ever seen.

I have a similar poster to this one, gotten from an issue of Newtype, except it doesn't have Mami and Kyubey in it

This is edited offical art. There are a bunch of versions of it already.

Niko01 said:
T-this has to be an official art, right? It looks too different from Torinone's works.

That's kind of the point of a style parody.