This isn't a recap. It's what happens when a studio gets permission to completely demolish its own movie and rebuild it as pure absurdist comedy, with Shana shrunk down to the size of a action figure watching her own story fall apart around her. The distortion isn't a bug, it's the point, the show is laughing at itself, at fanservice, at the medium itself. If you loved Shana enough to sit through the movie, this special exists to mess with your head about whether you should have taken any of it seriously in the first place.
A miniaturized Shana finds herself caught in a warped version of the movie's events, where the familiar plot is twisted in comedic ways. Scenes from the film play out again with the story bent out of shape and the heroine shrunk to a tiny size. The special is a lighthearted companion piece to the film, packaged with the director's cut special collection DVD of the Shakugan no Shana movie.