When we are trying to study Kuniyasu’s artistic activity in more details two main problems currently do not allow us to determining the place of this master in the process of the emergence and development of the Sagami School. The main problem is that no one of the confirmed work of this master has not been preserved to our times. The second problem is that Kuniyasu was listed amount Shintōgo Kunimitsu’s sons and sometimes being confused with his another son: Daishinbō. In addition to this, many old manuscripts indicate that Kuniyasu was a skilled engraver, and this skill has always been traditionally considered an attribute of Daishinbō.
Markus Sesko in his Index of Japanese Swordsmiths, 2012 provides the follow information about Kuniyasu:
Kuniyasu (國泰), Gen ́ō (元応, 1319-1321), Sagami – „Kuniyasu“ (國泰), according to transmission the third son of Shintōgo Kunimitsu (新藤五國光), it is said that he also signed with „Kunimitsu“ (國光), first name „Tōsaburō“ (藤三郎), one theory says that he was the same smith as Daishinbō (大進坊) – see also Daishinbō (大進坊), Shōwa (正和, 1312-1317), Sagami.
The most important old manuscripts contain the following information about Kuniyasu:
Kotō Meizukushi Taizen (古刀銘盡大全), Volume 2, p.12/1:
Around Shōō (1288-1293), son of Kunimitsu, signed later as Kunimitsu too, Shintōgo Saburō (三郎). Born in Kenji one (1275). Died in Kenmu four (1338) at the age of 64.
Kokon Meizukushi Taizen (古今銘尽大全), Volume 1, p. 9/1:
Kuniyasu (國泰), son of Kunimitsu, called Daishinbō (大進房), skilled carver, uncle of Masamune.
Tōken Kantei Hikketsu (刀剣鑑定秘訣), Volume 3, p. 26:
Kuniyasu was the younger brother of Kunihiro and his first name was Saburō (三郎). His workmanship basically follows the style of his older brothers Kunishige and Kunihiro. Quality of Kuniyasu’s works was at least of the same level comparing to his older brothers; neither inferior, no superior quality.
Kokon Wakan Banpō Zensho (古今和漢万寶全書), Volume 11(2), p. 55/1:
Swordsmith Kuniyasu; this name was his pseudonym; he was placing his name right below the first mekugi-ana; his horimono ends on the habaki-moto area; he borne the name Daishinbō (大進房) also; son of Kunimitsu; Kuniyasu was a very skilled engraver; uncle of Goto Nyudo (五郎入道); his artistic activity period is regards to 正元 1259-1260.
Honchō Kaji Kō (本朝鍛冶考), Volume «Tiger», p. 5/2:
Kunimitsu’s 3rd son, Shintōgo Saburō, he was born in the 1st year of the Kenji era (建治, 1275) and died in his 64th year in the 2nd year [error, should be 4th year here] of the Kenmu era (建武, 1335), he signed later as Kunimitsu, he was Buddhist monk with name Daishinbō (大進房).
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