The first-generation Izumi no Kami Kunisada (和泉守国貞), also known as Oya Kunisada or Chika-Kunisada, was born in Province and is said to have studied under Kunihiro in Kyoto. The consistently qualifies this tradition: "judging from the style of his early works and the manner of his signatures, it is thought that in actuality he received guidance from Echigo no Kami Kunitsugu, who stood as a senior figure among Kunihiro's circle." When Kunihiro died in Keicho 19 (1614), Kunisada was only twenty-five years old. Thereafter, together with his fellow disciple the first-generation Kawachi no Kami Kunisuke, he relocated to Osaka, and in Genna 9 (1623) he received the title Izumi no Kami. It is transmitted that in his later years he took the tonsure and called himself Dowa, dying at the age of sixty-three in Keian 5 (1652). Together with Tsuda no Kami Sukehiro and his own son Shinkai, Kunisada stands at the foundation of the Osaka tradition.
The in Kunisada's work is characteristically a tightly forged with "exceedingly fine, dense " and finely appearing , producing steel that is praised as "notably clear" and "bright." The begins with a -- a hallmark feature -- above which the temper develops into mixed with and slightly pointed elements, or alternatively a -based pattern mixed with . The is deep, adheres thickly, and and run throughout; appears around the , and the characteristically finishes in with , returning with a long and . The notes that Kunisada's early works "faithfully inherit Kunitsugu's approach," sometimes even modeling the smith Izumi no Kami Kaneyuki, while his mature manner develops a "calm and unforced character closer to that of Kunihiro." Features such as "the in -sagari style and the frequent appearance of " are identified as distinctive traits of Oya Kunisada, and his carved dragons display the celebrated "donguri-me" -- acorn eyes.
The reserve particular praise for the depth and clarity of Kunisada's , calling it "deep and splendid" and observing that "examples in which the is as deep and the as thick as in this work are uncommon." His output encompasses , , , and even the rare and -tempered examples -- a breadth that demonstrates exceptional versatility. The collaborative with Sukehiro is described as a work "that cannot be omitted in the study of Osaka ," while pieces bearing the late cursive sosho signatures remain subjects of scholarly debate regarding proxy authorship. Across all phases of his career, Kunisada's blades are characterized by "a powerfully impressive character" -- a forging of excellent quality married to a tempering domain of depth, luminosity, and vigorous internal activity.