The term “gusuku” means castle in Okinawan dialect. On my trip to Okinawa, I have learned that there are many castle sites in Nanjo city. I have visited Zagimi Castle and Shuri castle. To my understanding, Shuri castle is the most popular one and it is an imperial castle that governed over Ryukyu empire over 500 years. The architecture of Shuri castle was actually influenced by the culture of China and Japan everywhere. It was restored in 1992 because it was badly damaged during the Pacific War.
I wouldn’t necessarily call all of them “castles” but I would call them military fortresses/palace. Due to their giant outer walls that barricade all around the premises. When I hear the term castle I think of a giant mansion that is fancy, built of all stone, well structured, and looks fit for a king or royal family. When I compare Nakijin to something like Shuri … I’d say that Shuri looked a lot more like castle than Nakijin.
One thing that definitely stood out to me right away was that Nakijin does not have a yagura like the Himeji castle. Yagura are defense platforms. Najijin has a lot of stone walls that surround the entire area. The Aji lords built it in the 13th century. And for these ancient walls to still be standing … I am impressed. Which is why I would call it a fortress! With stonework that was quite solid it almost looks impenetrable.