The Kamiizumi clan was a Japanese clan that originated in Kai province

Kai Province

, also known as , is an old province in Japan in the area of Yamanashi Prefecture. It lies in central Honshū, west of Tokyo, in a landlocked mountainous region that includes Mount Fuji along its border with Shizuoka Prefecture....

 primarily during the Sengoku Period

Sengoku period

The or Warring States period in Japanese history was a time of social upheaval, political intrigue, and nearly constant military conflict that lasted roughly from the middle of the 15th century to the beginning of the 17th century. The name "Sengoku" was adopted by Japanese historians in reference...

 of the 16th century. The Kamiizumi clan served loyally under the local family of Uesugi

Uesugi clan

The was a Japanese samurai clan, descended from the Fujiwara clan and particularly notable for their power in the Muromachi and Sengoku periods ....

 throughout the course of the 16th century.

One very famous member of the clan of note was Kamiizumi Hidetsuna. Hidetsuna could be considered technically to be the creator of the Yagyū Shinkage ryū fighting style. This was through the fact that Yagyū Muneyoshi

Yagyu Muneyoshi

Yagyū Sekishūsai Taira-no-Munetoshi was a samurai in Japan’s Sengoku period famous for mastering the Shinkage-ryū school of combat, and introducing it to the Tokugawa clan.-Early life :...

 (the father of the famous Yagyū Munenori

Yagyu Munenori

was a Japanese swordsman, founder of the Edo branch of Yagyū Shinkage-ryū, which he learned from his father Yagyū "Sekishusai" Muneyoshi. This was one of two official sword styles patronized by the Tokugawa Shogunate...

) served as a prime student under Hidetsuna. Through the fighting style that Hidetsuna passed down to Muneyoshi assisted in the birth of the Shinkage-Ryū.