* Image is for illustrative purposes only.Sekiyado Castle
関宿城
Sekiyado Castle is a historic castle in Kantō dating from the Built around 1528 (Kyōroku era), whose lord was Koga Kubō (Yanada clan) / Hōjō clan / Hisamatsu-Matsudaira clan.
Overview
Strategic Point of the Kantō Plain
Sekiyado Castle is a water fortress located at the confluence of the Tone and Edo Rivers, and is said to have been built by Yanada Narisuke, who served Kōgaku Kubō Ashikaga Shigeuji in Chōroku 1 (1457). This location, where three major rivers—the Tone, Edo, and Kinu—converge, served as a strategic point for water transport in the Kantō region, making it the site of intense struggles throughout the Sengoku period. So great was its geopolitical value that it was said, "Whoever controls Sekiyado controls the Kantō."
Sengoku Warfare
Sekiyado Castle became the stage for a three-way contest for control among the Hōjō clan, Uesugi Kenshin, and Takeda Shingen. Kenshin repeatedly led expeditions into the Kantō region from the Tenbun through Eiroku and Genki eras, and became deeply involved in the struggle for control of Sekiyado Castle. When the Yanada clan sought Kenshin's support to counter the Hōjō, Sekiyado Castle became the front line between the Hōjō and Kenshin's allied forces. Records remain of Kenshin personally leading an expedition in Eiroku 7 (1564) to relieve Sekiyado Castle. In Tenshō 2 (1574), Hōjō Ujimasa conquered Sekiyado Castle, and thereafter it functioned as an eastern base for Hōjō control of the Kantō.
Sekiyado in the Tokugawa Period
After the fall of the Odawara Hōjō in Tenshō 18 (1590), Sekiyado came under Tokugawa control, and Matsudaira Yasumoto of the Kumatsu Matsudaira clan was appointed as daimyo. Established as Sekiyado domain, this castle served as an important management point for water control of the Tone River and the transport of goods to Edo for the Edo shogunate. In the castle town, water transport business flourished, and products from throughout the Kantō were transported to Edo via Sekiyado. By the late Edo period, the Kuze family, as lords of Sekiyado domain, rose to prominence—producing senior councilors (rōjū) and wielding considerable influence in the shogunate's government.
Sekiyado Castle Today
After the Meiji Restoration, the castle was abandoned; subsequently, most of its remains were lost due to Tone River modification projects and flooding. In 1995 (Heisei 7), the Chiba Prefectural Sekiyado Castle Museum opened at the current site; with its three-story exterior modeled on a castle keep, it displays exhibits on the river culture of the Tone and Edo Rivers and the history of Sekiyado. From the museum's rooftop observation deck, visitors can enjoy views of the majestic flow of the Tone River and Mount Tsukuba, experiencing the geographic character of the former water fortress. The surrounding area includes green space developed as Sekiyado Castle Ruins Park, preserving the memory of the former water fortress.
Connection to Swords
Sekiyado Castle witnessed the clash of three major Kanto powers — the Yanada (Koga Kubō loyalists), the Hōjō, and Uesugi Kenshin — each of whom held strong swordsmanship traditions. The Hōjō clan patronized Sagami Province swordsmiths who worked in the prestigious Sōshū tradition, while Uesugi Kenshin was known as an avid sword collector whose estate contained exceptional Bizen and Sōshū pieces. The Tone River's logistics network connecting Kanto and Tohoku made Sekiyado an important hub for the regional sword trade.
Highlights
- Chiba Prefectural Museum of Sekiyado Castle (castle-style building, river culture exhibits)
- Rooftop observatory with panoramic views of the Tone River and Mount Tsukuba
- Sekiyado Castle Site Park (riverside greenery preserving the water-castle atmosphere)
- Tone River / Edo River confluence (strategic waterway crossroads since the Sengoku era)
- Riverside cycling routes along the Tone River
* Opening hours and admission fees are subject to change. Please check the official website before visiting.