Sunpu Castle in Shizuoka, probably one of the most important castles in Shizuoka Prefecture.
Aerial view of Himeji castle, Hyogo, Japan 姫路城大天守 南西より
Kushima Castle in Nagasaki, a great place to see cherry blossoms in the Spring
Inside of Japanese castle, Hiroshima-jo castle
Japanese castles I've visited: #58 Matsumae Castle in Hokkaido. Pretty much the only "real" Japanese castle left in Hokkaido! Read more about it here in my blog: http://zoomingjapan.com/travel/matsumae-castle/
Roof detail of Himeji Castle, Japan
Japanese castles I've visited: #64 Nagahama Castle in Shiga Prefecture. Not too far from Hikone Castle, you can easily visit both in one day! ;)