Mogami Clan (最上氏)

The Mogami clan was a branch family of the Shiba clan (kanrei [shogunal deputy]) that belonged to the same family of the Ashikaga clan of Seiwa-Genji (Minamoto clan). It served as Ushu Tandai (supervisors for the civil government and military affairs in Mutsu Province) and became daimyo (Japanese territorial lord) of Dewa Province later. It was also called the Shiba-Mogami clan or Shiba-Dewa family.


The Shiba clan in which the Mogami clan had roots was supposed to succeed the Ashikaga clan, but was disinherited through the intermediation of the Hojo clan, and moved out and set up a new branch family of the Ashikaga family. In the Enbun era (1356 to 1360) of the period of the Northern and Southern Courts (Japan), Kaneyori SHIBA, a son of Iekane SHIBA, Oshu Kanrei (governor of Oshu), which was a branch of the Shiba clan, moved to Yamagata as Dewa no kuni Azechi and built Yamagata-jo Castle as his headquarters. He was permitted to have yakata (an honorific title) and call himself Mogami yakata by the Muromachi bakufu, and called himself the Mogami clan. Since he ruled Yamagata, he was often called the Yamagata clan ("Seishi Kakei Daijiten" [a large dictionary of Japanese surnames] by Akira OTA).

Although it reached the high watermark in the Muromachi period, it came to decline due to frequent inter-clan conflicts, such as one with the Tendo clan, and Yoshisada MOGAMI was defeated by the Date clan in the battle of Hasedo-jo Castle in 1514 and became under control of the Date clan temporarily. After the death of Yoshisada, Yoshimori MOGAMI who was invited from a branch family of the Nakano clan became a puppet in the hands of the wife of Yoshisada from the Date clan who held the rein of power instead of him.

When Tenbun no ran (Tenbun Rebellion) occurred in the Date clan in the Sengoku period (Japan), Yoshimori MOGAMI became independent of the Date clan and began to become daimyo (Japanese territorial lord). Yoshiaki MOGAMI, a son of Yoshimori, exterminated the Tendo clan that was his branch line and the Sagae clan in the neighborhood and dominated the Murayama County. In addition, he made conflicts with the Daihoji clan in the Shonai region and powers in the neighborhood. Yoshihime, a sister of Yoshiaki MOGAMI, got married to Terumune DATE and gave birth to Masamune DATE.

In 1590, he served Hideyoshi TOYOTOMI who was trying to establish himself as ruler of the country after the conquest and siege of Odawara, was approved of the main domain, lived in Yamagata-jo Castle and had a fief of 240,000 koku. He gained Ogachi County in 1591. Yoshiaki was forced to present his daughter Komahime to Kanpaku (chief adviser to the Emperor) Hidetsugu TOYOTOMI as a concubine, but she and Hidetsugu were killed by Hideyoshi. Although Yoshiaki had approached Ieyasu TOKUGAWA before that, he distanced himself from the Toyotomi clan and approached the Tokugawa clan. When the Battle of Sekigahara occurred after the death of Hideyoshi, Yoshiaki fought the Uesugi clan as the 'eastern' army (the battle of Hasedo-jo Castle). He also fought the Onodera clan in the neighborhood north and subdued the Ueura County (Hiraka County, Ogachi County).

He gained more territories as a reward for the Battle of Dewa in the Keicho era, which was associated with the Battle of Sekigahara, gained the current whole Yamagata Prefecture and Yurihonjo City, Akita Prefecture (which were replaced by Ogachi County and Hiraka County by agreement with the Satake clan in 1602), became Daidaimyo (a feudal lord having a greater stipend) with a total fief of 570,000 koku (the actual yield was considered 1,000,000 koku) and reached the high watermark again. In the Edo period, a race for successor of Yoshiaki occurred and the first son Yoshiyasu MOGAMI was assassinated. Internal conflicts did not stop since then and a Mogami squabble occurred in the generation of Yoshitoshi MOGAMI, a grandson of Yoshiaki.

Yoshitoshi lost the confidence of his family members and the Mogami clan was deprived of his fief for the reason of the trouble by the order of the bakufu in 1622. Since the head family, the Shiba-Buei family, had fallen, the extinction of the Mogami clan following the Shiba clan was lamented and the Mogami clan was given again with a fief of 10,000 koku in Omi Province. After the death of Yoshitoshi, the fief of his son Yoshitomo MOGAMI was reduced to 5000 koku because he was very young, and his descendents survived as hatamoto (bannermen) kotaiyoriai (alternate yoriai, a family status of samurai warriors in the Edo period).

Yoshitada YAMANOBE, the fourth son of Yoshiaki, was finally promoted to Karo (chief retainer) of Mito Province, and his descendents served as vassals and played an important role in the domain duties ('Hyogo YAMANOBE,' the captious kunigaro [the chief retainer in charge of the fief in the absence of the lord] of Mito Province, who was played by Ryutaro OTOMO, Hideo TAKAMATSU, or Tetsuro TANBA, in the TV historical play 'Mitokomon' (Panasonic drama theater) modeled after Yoshikata YAMANOBE, a son of Yoshitada).

Descendents of Mitsuhiro MATSUNE, a nephew of Yoshiaki, survived as a house of chief vassal of Uwajima Province, and Zusho MATSUNE assisted Munenari DATE at the end of the Edo period. Toyojo MATSUNE, a disciple of Soseki NATSUME and Haiku poet, was a grandson of Zusho.

Different theories about the genealogy of the Mogami family

There are different theories about the genealogy of the Mogami family. In particular, some say that the family tree after the death of the fourth Mitsuie to Yoshisada lacks credibility.
Main different views are as follows:

Yorimune MOGAMI, an older brother of Yoshiharu MOGAMI, took over as head of the family after the death of Mitsuie MOGAMI, and Yoshiharu took over as head of the family after the death of Yorimune.

Yoshiaki MOGAMI was not a younger brother of Yoshiharu or Yorimune, but a son of Yoshiharu.

Mitsuuji MOGAMI was not an adopted son of Yoshiaki, but his biological child.

Yoshiatsu MOGAMI was a younger brother of Mitsuuji.

Although there are different view of children in the genealogy, Yoshisada MOGAMI and the subsequent descendents were considered credible. However, some researchers had objections to the branch families from Yoshimori MOGAMI.

Yoshinao KAMINOYAMA was not a son of Yoshiaki MOGAMI, but of Yoshimori, and he was a different person from Mitsuhiro MOGAMI (the fifth son of Yoshiaki) though he was considered the same person as Mitsuhiro.

There was another brother named Yoshie MOGAMI between Yoshiaki MOGAMI and Yoshitoki NAKANO (fictional person?).

In addition, there is a different theory about children of Yoshimori and Yoshiaki.


The present family head is Kimiyoshi MOGAMI who lives in Kyoto Prefecture.

The Mogami Yoshiaki Historical Museum is located in Yamagata City, Yamagata Prefecture, which was headquartered by the Mogami clan from the period of the Northern and Southern Courts (Japan) to the early Edo period, and the museum contains historical documents regarding mainly the 11th family head, Yoshiaki MOGAMI.

[Original Japanese]