Hi jguay!
first: the ghost of the samurai only exists if you have the "samurai-quest" - so at your first time it was ok, that he was not around...
second: the graveyard is on the left side of Shurugeon Castle, you have to swim through the first pillar and then exit to the left side... there comes a small way in the woods. The ghost appears on your left side, at a little clearing.
I hope that helps...
Silaya