The castle was erected in the 1600s-1610s under Fukushima Masanori, who granted it and an associated 8,131 koku fief to his retainer Ôzaki Genba, who then ruled that territory with some 342 retainers of his own under him. The castle originally boasted a three-story tower keep (tenshu), a sizable main gate (Ôtemon), and yagura. The keep was torn down in 1619 in accordance with the "one castle per domain" policy imposed by the Tokugawa shogunate, but the gate and yagura mansion (yashiki) survived the first century of the Edo period, up until they were lost in a fire on 1711/1/13.
After Fukushima Masanori was replaced by Mizuno Katsunari as lord of Fukuyama in 1619, Katsunari named his son Mizuno Katsutoshi to be lord of Tomo. Katsutoshi was to be the last "lord" or castellan of Tomo, being replaced by Hagino Shin'emon, who became the first of a long line of Tomo bugyô (Tomo Magistrates), who occupied the mansion (yashiki, formerly known as the "castle," or oshiro) and oversaw the administration of the port-town from that time forward.
The bugyô's mansion sat up against a hill or mountain to the south, and was fronted by moats to the north and east. A castle gate with an irimoya-style roof stood atop stone foundations, and there was a residence for ashigaru on the site as well. All of this was destroyed, however, in a fire on 1711/1/13. The mansion was over nine tan in size (75 by 36 1/2 bays).
The former site of the castle is today home to the Fukuyama City Tomonoura History Museum.
- Aono Shunsui 青野春水, "Edo jidai Tomo-chô no seiritsu to kôzô" 江戸時代鞆町の成立と構造, Tomo no tsu Nakamura-ke monjo mokuroku IV 鞆の津中村家文書目録 IV (2009), 252-253.