Ashino Sukeyasu (Yamato-no-kami) served as a bushō during the Sengoku and Azuchi-Momoyama periods.  Sukeyasu was the fifteenth head of the Ashino clan based in Ashino in the Nasu District of Shimotsuke Province.

The Ashino were an illegitimate branch of the Nasu clan of Shimotsuke and counted among the Seven Clans of the Nasu.

Sukeyasu was born as the eldest son of Ashina Suketoyo, the fourteenth head of the Ashino clan.

In 1552, upon demand of Satake Yoshiaki with whom the Ashino were allied, he invaded the territory of the Shirakawa-Yūki clan in Shirakawa in the southern portion of Mutsu Province.  After assaulting their base at Komine Castle, he captured several enemy heads, set fire to surrounding residences, and withdrew.  Owing to these contributions, Yoshiaki granted Sukeyasu land in Ishii and Kawakami in the Shirakawa District.  After meeting Yoshiaki, while returning to his territory, he encountered an ambush set by members of the Iōno clan, but Sukeyasu detected the plan and scattered the enemy forces.

Sukeyasu’s younger sister became the formal wife of Nasu Suketane.  Meanwhile, Sukeyasu was granted landholdings by Yoshiaki, indicating that the Ashino clan operated with a degree of independence at this time.  In 1560, at the Battle of Odakura, Sukeyasu led an army in support of Suketane to intercept allied forces from the Shirakawa-Yūki and Ashina clans invading Mutsu.  Following the arrival of reinforcements including Ōzeki Takamasu and Senbon Suketoshi, the forces led by Sukeyoshi mounted a counterattack, repelling the invaders.

That same year, after Takamasu betrayed the Nasu clan, incited followers of the Upper Nasu family, and colluded with Satake Yoshishige, Sukeyasu joined forces with Takamasu, cutting ties with Suketane and siding with the Satake.  Nevertheless, at Mount Jibuuchi, Mount 大崖, and Kirigasawa, the allied forces of the Satake and Upper Nasu family lost several battles to Suketane.  In the ninth month of 1568, followers of the Upper Nasu settled with Suketane, severed ties with the Satake, and fell under the command of the Nasu clan.

Later years

In the third month of 1585, Sukeyasu, together with his son, Ashino Moriyasu, and lord, Nasu Sukeharu, confronted the allied forces of Shionoya Yoshitsuna and Utsunomiya Kunitsuna at the Battle of Usubagahara.  In this conflict, Sukeyasu had Moriyasu serve in the vanguard, and after valiant fighting by the Ashino forces, the tide of the battle favored the Ashino.  From a weakened position, a retainer of the Shionoya named Yamada Tokinari led a suicide mission and charged forward in a bid to strike Sukeharu.  Sukeyasu was momentarily exposed but a retainer of the Ashino, Kanda Jirō, brought down Tokinari and took his head so Sukeyasu was spared.

Soon thereafter, it appears that Sukeyasu transferred the headship of the clan to Moriyasu.  In 1590, during the Conquest of Odawara, when Moriyasu served under Toyotomi Hideyoshi, Sukeyasu did not join him.  After retiring, he adopted the monk’s name of Ikyūsai.

On 12/3 of Bunroku 3 (1594), Sukeyasu died at the age of sixty-six.