Aisu

The Aisu, also written Aiso in old records, were a medieval seafaring warrior clan of the Kii and Ise region; their genealogy was claimed from the Takeda line of the Seiwa Genji. They are said to have led a naval force in the Mongol Kōan campaign of 1281. The Ise branch held Gokasho Castle and, under the sway of the Kitabatake, joined trade missions to Ming China from 1451.

The clan's famed Aisu Hisatada, known as Ikōsai (1452-1538), founded the Kage-ryū school of swordsmanship after martial pilgrimage, traditionally including a voyage to Ming China. The swordsman Kamiizumi Nobutsuna was counted among his disciples.

His son Munemichi inherited the school and entered the service of Satake Yoshishige. After the destruction of the Kitabatake the Aisu also served the Satake and adopted the surname Hirasawa. When the Satake were transferred to Dewa after the Battle of Sekigahara in 1600, the Kage-ryū head house moved north with them.