I join your chorus of disliking Index's role in this. While it's totally believable she would be thoughtless enough to enter the suspicious building, it's still annoying her role was reduced to such an object and Touma's actions dictated by trying to rescue her (gee, I think I've seen this plot somewhere before). It would have been much better if Index had remained out of the picture like she was supposed to, and Touma had decided to march in simply to kick some ass.