It is easy to use the JR East Pass or JR Railway Pass to travel to it because the castle is near the Shirakawa JR Station by walking in 3 mins.
I had a bad luck while I invited there because the castle was repairing which is caused by the earthquake on March 11th, 2011, but I still could see the Tenshu at the entrance of the castle.
Because the repairing work, it cannot be allow to visit the inside of it.
The repair would be finished util May, 2016.
As one of the top 100 castles, it shows the proof of Japan history and the power of human. There is a park around the castle called Shiroyama Park, and it is clean and very quiet even if the castle was repairing. I couldn't enter it was my only regret on this trip.