The Agakita Group refers to a group of wealthy kokujin, or provincial landowners, who defended their local authority in the northern portions of Echigo Province from the Kamakura to Sengoku periods. Agakita refers to the region to the north of the Agano River in Echigo.
The clans comprising the Agakita Group can be categorized based on their place of origin, including extended families of the Chichibu of Koizumi, the Miura of Okuyama, the Sasaki of Kaji, and the Ōmi of Shirakawa. During the Kamakura period (1192 to 1333), wealthy families including the Chichibu clan of Musashi Province, the Miura clan of Sagami Province, the Sasaki clan of Ōmi Province, and the Ōmi of Iga Province moved into the Agakita region of northern Echigo and became of the lords of their respective shōen, or manors. Over the generations, their descendants strengthened their control over the area, and each clan evolved into provincial landowners adopting surnames based on the place names of the lands under their governance. Collectively, these extended families came to be referred to as the Agakita Group.
Specifically, the extended families were comprised of the following: (i) the Chichibu clan included the Honjō (main family), the Irobe, and the Ayukawa; (ii) the Miura clan included the Nakajō (main family), and the Kurokawa; (iii) the Sasaki clan included the Kaji (main family), the Shibata, the Takemata, and the Ijimino; and (iv) the Ōmi clan included the Yasuda (main family), the Suibara, and the Shimojō. The Kawamura clan of Sagami Province moved to Echigo after their appointment as the lord of the Arakawa administrative area which was a provincial governorate, adopting the name of the Tarumizu clan in the Muromachi period. The details of the Ōkawa clan are uncertain, but believed to have originated from dogō, or a small-scale landowner.
The Agakita Group held a strong sense of autonomy perhaps owing to their governance of the region dating from the Kamakura period. From the Nanboku period, after the Uesugi clan became the military governors and the Nagao clan became the deputy military governors of Echigo, these clans frequently clashed with members of the Agakita Group. This was a contributing factor to the instability of the political environment in Echigo from the Muromachi period to the Sengoku period. Date Tanemune, the sengoku daimyō of Mutsu Province, sought to expand his influence in Echigo Province by proposing to Uesugi Sadazane (the military governor of Echigo) to adopt Tanemune’s third son, Tokimunemaru (later known as Date Sanemoto). On the side of the Date clan, this proposal was opposed by, among others, Tanemune’s eldest son, Date Harumune. Meanwhile, on the side of the Uesugi, the plan was supported some members of the Agakita Group led by Nakajō Fujisuke, but opposed by other members led by Honjō Fusanaga, Irobe Fujinaga, and Ayukawa Kiyonaga. The clashes stemming from this proposal persisted from 1542 to 1548 and, collectively, are known as the Tenbun Conflict. This led to the rupture of the Agakita Group and a decline in their autonomy. Ultimately, in the course of the Nagao clan rising to the level of sengoku daimyō, the members of the Agakita Group were folded into their band of retainers. Nevertheless, among the retainers, the Agakita Group maintained a special presence and significant military capability.
Based on military chronicles, members of the Agakita Group comprised approximately thirty percent of the Uesugi army. The Agakita Group played a prominent role in the Fourth Battle of Kawanakajima in 1561. After the conflict, Uesugi Kenshin awarded four members of the Agakita Group, namely, Irobe Katsunaga, Yasuda Nagahide, Nakajō Fujisuke and Tarumizu Genjirō (Arakawa Nagazane), with a special letter of commendation for their loyalty amidst the loss of many fellow soldiers.
Even after surrendering to the Nagao (Uesugi) clan, certain influential figures including Honjō Shigenaga, Shibata Shigeie, and Ijimino Nobumune came into conflict withe the Uesugi. The Honjō clan was permitted to return to the service of the Uesugi, but the Shibata and Ijimino were decimated. Many families left their ancestral lands, obeying orders to transfer from Aizu in Mutsu Province to Yonezawa in Dewa Province, and, in the Edo period, served the Yonezawa domain. Among those, the Honjō, the Irobe, the Nakajō, and the Takemata clans served as chief retainers and other leading roles within the Yonezawa domain. In the early Edo period, the Tarumizu clan became retainers of Honda Masashige and served the Kaga domain.
The Yamaura clan (including Yamaura Kagekuni based at Sasaoka Castle) and the Chisaka clan (including Chichibu Kagechika based at Hachimari Castle) controlled the area of Shirakawa from the Muromachi period. The Yamaura were a branch of the Uesugi family and the Chisaka headed the band of retainers of the Inugake-Uesugi family (according to one theory, were a branch of the Inugake-Uesugi). Accordingly, from the time of their move to Echigo, these clans were of the same status as the Nagao clan, serving as chief retainers of the Uesugi military governors, so were not included in the Agakita Group.