Katana is a traditional combat sword - some versions conflict about whether
the 'official katana' is straight or curved - but I take the curved
version.
It is generally a two handed slicing blade, but ninjas have been known to
wield two. It's size can range from 3 to 5 feet or so.
I was wondering where you got that fact about the use of two katanas. In
all the literature I've have seen and read I've heard of no mention of that.
I've always heard that was simply a "myth" and popularized in comics like
TMNT or other anime.
-Deunan