This is a list of surnames in which the usage is Japanese; and the meaning contains the keyword castle.
Ōshiro 大城, おおしろ JapaneseFrom Japanese
大 (ō) meaning "big, great" and
城 (shiro) meaning "castle". It is especially common on Okinawa.
Yūki 結城, ゆうき JapaneseFrom Japanese
結 (yū) meaning "tie, bind" and
城 (ki) meaning "castle".