Zangetsu posted picture scans from Muguruma @ 2ch in this post here- http://bleachasylum.com/threads/13562-Bleach-Movie-4?p=2520863&viewfull=1#post2520863
THis is the tiny bit that was written by Muguruma and translated by sheetz, I believe:
He committed crimes for his younger sister when he was alive and was sent to Hell.
He hates a band of criminals lead by someone named Akihasu (or something like that). He frees Karin from their grasp.
And so he goes with Hell to fight along with ichigo.
Akihasu shoots fire a fire lance and wields a crimson lotus sword. He launches a scheme to use a secret ability on Ichigo.
Translation by sheetz posted by Syn in IR FC here: bleachasylum.com/threads/16606-v45-Death-a
EDIT: Decided to repost some of the previous things we've heard about the movie, just to have it in one place.
From this earlier poster:
The box in the bottom corner reads: Kubo Sensei's full cooperation!
This time we had him participate in the movie from the beginning. Because he had a number of meetings with the screenwriters where details were decided upon, it is a work filled with strong emotion. In the original work the "Hell" theme only appeared in words, and with no current plans for its portrayal we thought it would be interesting to step over there and had him discuss it with them.
At first we didn't imagine what kind of work it would be, but the first time we knew it would be interesting is when we saw character designer Kudo-san's images of Hell. They were very fresh, which is why we think you'll be pleased if you pay attention to the backgrounds when you see the movie.
Aaaaand a movie summary from BleachExile: Movie summary: "HELL". is the place where a person is sent to who committed violent crimes when they were alive. SHINIGAMIs are forbidden to go there. One day prisoners revolt and make their escape to the KARAKURA-town where Ichigo and his friends live in. Ichigo and his friends are defeated one after the other by prisoners with overwhelming power. A mystery man appears ("KOKUTOO) who comes to their rescue. With Kokutoo leading the way Ichigo, Rukia, Uryuu, and Renji marches into HELL to save the world.
Now an endless, desperate struggle breaks out between Ichigo and his friends with the TOGABITO!"