Also known as: Shishisai (止々斎)

Son of Ashina Morikiyo and 16th generation lord of the Ashina Clan who probably became head of the clan around 1537, which is around the time that he married a daughter of the Date Clan and formed an alliance with Tamura Takaaki.

He expanded the domain of the Ashina and did much to improve the clan's economic condition, thereby bringing about the golden age of the Ashina.

Moriuji turned over the rule of the clan to his heir Ashina Morioki in 1561 and retired to Iwasaki Castle, shaving off his hair and taking the name of Shishisai. However, he retained power over political and military affairs.

In 1575 when Ashina Morioki died without an heir, and because Moriuji had no other heirs, he adopted a hostage of the clan: Nikaidou Moritaka, the son of Nikaidou Moriyoshi, and married him to Morioki's widow. Moritaka then became Ashina Moritaka and the next clan head.

Moriuji died in 1580 at the age of 60. With him ended the golden age of the Ashina; a mere 9 years later, the clan would be destroyed by Date Masamune.