as far as i know only the Queen's Chest holds a chance to contain the Muramasa ... found it there aprox 30% the tries .. (reloading a game just before entering the upper castle)..
for the bushido -> sometimes the rapax assassin in Marten's Bluff dropps one ..
in Bayjin Shallows you can find the *light* sword ... also not tooo bad for a samurai ...
