The Honma clan is a Japanese clan that ruled the province

Provinces of Japan

Before the modern prefecture system was established, the land of Japan was divided into tens of kuni , usually known in English as provinces. Each province was divided into gun ....

 of Sado

Sado Province

was a province of Japan until 1871; since then, it has been a part of Niigata Prefecture. It was sometimes called or . It lies on the eponymous Sado Island, off the coast of Niigata Prefecture ....

 between the 12th and 16th century.

Yoshihisa Honma was appointed shugodai

Shugodai

were officials during feudal Japan.Shugodai were representatives of provincial shugo when the shugo could not exercise his power, being often away from his province. Unlike shugo, who were appointed from the central power, shugodai were locally appointed....

 of Sado in 1185. The clan established its rule from Sawata.
The clan gave birth to two new branches, the Hamochi-Honma and the Kawaharada-Honma. Those two branches eventually prevailed over the head clan and opposed each other. Uesugi Kenshin

Uesugi Kenshin

was a daimyo who ruled Echigo province in the Sengoku period of Japan.He was one of the most powerful lords of the Sengoku period. While chiefly remembered for his prowess on the battlefield, Kenshin is also regarded as an extremely skillful administrator who fostered the growth of local industries...

, ruler of the Echigo Province

Echigo Province

was an old province in north-central Japan, on the shores of the Sea of Japan. It was sometimes called , with Echizen and Etchū Provinces. Today the area is part of Niigata Prefecture, which also includes the island which was the old Sado Province. This province was the northernmost part of the...

 at the time, settled the ongoing conflicts between Hamochi-Honma and Kawaharada-Honma. His death sparked a new rows of hostilities between the two branches, but Uesugi Kagekatsu

Uesugi Kagekatsu

was a daimyo during the Sengoku and Edo periods of Japanese history. The son of Nagao Masakage and husband of Uesugi Kenshin's elder sister, Aya-Gozen. After his father died, he was adopted by Kenshin....

invaded Sado in 1589, putting an end to the ruling of the clan.