See my previous rant about romanization systems
here.
"Kannaduki" is the standard romanization under Kunrei-shiki, which is the "official" romanization system of Japan. That doesn't mean everybody uses it, but it's, uh, "official".
Kunrei is funny though, because it tosses a number of exceptions in there. "You use si, except in cases where somebody used shi already, in which case you use shi."
