her intestines. Since Yukari didn't pierce anything, that probably wouldn't even kill Reimu. But, she'd probably have to see Eirin or drink an Hourai Elixir to re-align it.
Ughhhh... I gut fish fairly often and I always try my best to NEVER squeeze the intestines. If you do, whatever leftover shit is inside will always squeeze out.
I suddenly have a deep hatred for Yukari... Minor, internal, intestinal problems hurt like hell, so Reimu probably wishes she was dead right about now. (and after reading some of the other comments, Reimu may or may not die from this...)