So I'm level 41 and I just got to the Jungle, but I haven't seen a Katana since level 30. I found a Frail Katana on the beach of the first area at around level 30 inside of a metal chest. Since then, I have been checking shops and chests and enemies and what-have-you, yet I still have not seen any other Katanas. Aside from Zed's Demise (I'm not that far yet), is there any certain way to obtain a Katana?
A little FYI
Xian Mei can perform a special attack when her first blade skill is upgraded. The skill is activated when you aim at a zombies head or neck, then Xian presses the blade against the zombies neck, causing roughly 1000-2000 damage.