The Oda Castle Ruins (小田城跡)

The ruins of Oda Castle

Oda Castle (小田城) was a flatland-style castle that once stood in what is now the Oda district of Tsukuba, Ibaraki Prefecture. As the name suggests, it served as the residence of the Oda clan (小田氏), who held power in the southern part of Hitachi Province (roughly corresponding to modern-day Ibaraki Prefecture) from the Kamakura period (1185–1333) through the Sengoku period (1467–1573).

The exact date of the castle's construction is unclear, and there are various theories about when the Oda clan established their base there. Some believe it began with Hatta Tomoie (1142–1218), the clan's founder, while others point to the fourth head, Oda Tokitomo — the earliest figure confirmed to have used the Oda name.

Hatta Tomoie was appointed shugo (military governor) of Hitachi Province by Minamoto no Yoritomo (1147–1199), the founder and first shogun of the Kamakura shogunate. However, during the late Kamakura period, as the Hojo clan rose to power, the Oda clan's territory was gradually reduced. By the end of the period, they had completely lost the shugo post.

During the Nanboku-cho period (1336–1392) — when the Northern Court, established by Ashikaga Takauji (1305–1358) in Kyoto, and the Southern Court, established by Emperor Go-Daigo (1288–1339) in Yoshino (in modern-day Nara Prefecture), fought for imperial legitimacy before the Southern Court ultimately conceded — Oda Castle served as a key Southern Court stronghold in the Kanto region. It was here that Kitabatake Chikafusa (1293–1354), a senior official of the Southern Court, wrote the Jinno Shotoki, a historical chronicle tracing imperial rule from the age of the kami (deities) to the reign of Emperor Go-Murakami (1328–1368), the second emperor of the Southern Court.

Under its 14th head, Masaharu, the Oda clan became the dominant power in southern Hitachi during the Sengoku period. However, surrounded by powerful neighbors — the Go-Hojo (Later Hojo) clan of Sagami Province, the Uesugi clan of Echigo, and the Satake clan in northern Hitachi — Oda Castle became the site of frequent battles. In 1569, the 15th head, Ujiharu, was defeated at the Battle of Tebaizaka, and the castle fell under Satake control until 1602, when the clan was relocated to what is now Akita Prefecture. The castle was subsequently abandoned.

The site was designated a National Historic Site in 1935.

A brief history of the Oda clan, along with excavated artifacts, is on display at the nearby Oda Castle Remains History Plaza Information Center (小田城跡歴史ひろば案内所).

Opening hours:
9:00 AM – 4:30 PM

Closed on:
Mondays (if a national holiday falls on a Monday, the museum will be open that day and closed the following day instead)
The day after national holidays
During the New Year holidays

Reference:

• つくば市教育委員会. (n.d.). 小田城跡歴史ひろば案内所. 国指定史跡 小田城跡歴史ひろば. https://www.city.tsukuba.lg.jp/material/files/group/156/oda.pdf