Iai/battodo is a traditional Japanese martial art. There are several schools, I've studied two prominently: Tenshin Shōden Katori Shintō-ryū and Toyama-ryū.
The basic idea is that the kata start with the sword sheathed, and they are mostly trying to reproduce situations that I would describe as self-defense with the sword. There are some rather major exceptions in KSR, there is at least one assassination kata and one for seconding seppuku.
I really love it.