Ippei Yasuzai was born in Hoei 5 (1708) as the second son of Nakamura Kiyofusa. Because the preceding headmaster Ippei Yasuyo had no biological heir, Yasuzai was adopted into the family in Kyoho 8 (1723) at the age of sixteen. When Yasuyo died at forty-nine in Kyoho 13 (1728), Yasuzai succeeded to the headship of the line at twenty-one. He lived longer than his adoptive father, dying at age seventy in An'ei 6 (1777); thus the period in which master and successor coexisted was brief. He initially signed his work as "Yasuharu" and also undertook and on behalf of others; combined with extended service duties for the warrior class, independently signed works by Yasuzai are comparatively few.
His workmanship strongly inherits the manner of Yasuyo and the Satsuma tradition. The is characterized by broad , thick , and ample , with rather deep . The forging shows tightly packed mixed with somewhat rough , tending toward a darkish overall tone; fine enters well. The is based on , with deep and thickly adhering including ; and appear. The rounded and file marks are also extremely close to Yasuyo's practice. Compared with his master, however, the internal activities within the are calmer and the tends in places toward becoming tight — features through which the assessors identify Yasuzai's individual character.
His finest designated works are praised as achieving a level of excellence comparable to that of Yasuyo himself. The 51st-session is singled out as a well-composed superior piece in which Yasuzai's particular flavor — that calmer, more tightly controlled — emerges most clearly against the inherited foundation of the Ippei house style.