Jirotaro Naokatsu was a disciple of Naotane and later became his adopted son. He served the Akimoto clan of Tatebayashi in Joshu (Kozuke Province) and resided at Shitaya in . At first he called himself Kazusa Taro, later adopting the name Jirotaro, though no works bearing the earlier signature have been observed. He died on the twenty-second day of the seventh month of Ansei 5 (1858), the year following Naotane's death, at the age of fifty-four. Within the Suishinshi line, the consistently identifies Naokatsu as the most capable craftsman after Naotane and Masayoshi, and a noted master in his own right.
Naokatsu's workmanship divides broadly into the - and - modes. His - works, modeled on the styles of Kanemitsu and Kagemitsu, are especially celebrated -- the note that among these "there are pieces that surpass even Naotane." In this manner, the shows tightly forged with fine , faint , and bright steel. The is typically a of -like flavor, mixed with angular elements, , and -ba, tending overall to ; long enter well, and the is bright and clear. , , and small appear. When compared with Naotane, Naokatsu's works "generally show a more bold and heroic ," with a tendency for the -flavored to become larger. His Nagamitsu copies demonstrate a distinct ability to evoke archaic atmosphere through restrained tempering set slightly lower than usual.
The designation records characterize Naokatsu's finest works as achieving "a level of brilliance that can stand alongside Naotane's masterpieces." One blade held in the Imperial Collection () further attests to the esteem in which his work was held. His - works, too, sometimes surpass Naotane, and the caution that the signature styles of master and disciple "vary greatly -- from bold large characters with thick chisels to fine small characters with thin chisels," making authentication a noted challenge.