The Ryokai lineage constituted an independent branch within the Rai school of Yamashiro Province, active from the late Kamakura period. Tradition holds that Ryokai studied under Rai Kunitoshi, with one account relating that he became Kunitoshi's adopted son; however, since dated works by Ryokai bear era inscriptions spanning Shoo (1288--1293), Kagen (1303--1306), Enkyo (1308--1311), and Ocho (1311), the NBTHK considers it more reasonable to regard him as a contemporary of Rai Kunitoshi -- "a swordsmith who established a different line and formed an independent lineage" rather than necessarily Kunitoshi's direct pupil. His son, Ryo Hisanobu, whose common name Kurozaemon no Jo is confirmed by a critically important tachi dated Kagen 2 (1304), carried the lineage into the early fourteenth century, with further works from the Tokuji and Enkyo eras. A joint work (gassaku) between father and son dated Kagen 3 (1305) survives and constitutes one of the most valuable documentary materials for establishing the internal chronology of the Rai school. Several generations bore the Ryokai name; in later times some are thought to have moved to Kyushu, and smiths signing "Ryokai" are found extending into the Muromachi period.

The workmanship of the Ryokai group shares clear continuity with the Rai tradition yet possesses a cluster of distinguishing traits that the NBTHK identifies as key points of appreciation. The forging characteristically shows a masame-gokoro -- a tendency toward straight grain -- in which a whitish shirake cast stands out conspicuously, frequently displaying shirake-utsuri or a faint nie-utsuri-like effect. The hamon is a calm, restrained chu-suguha, at times mixed with ko-choji, ko-gunome, or a shallow notare tendency, rendered in ko-nie-deki with well-formed ashi and yo. A hallmark trait shared across the group is that the nioiguchi of the suguha temper shows an urumi tendency -- a moist, soft quality -- particularly around the koshimoto. Compared with Rai Kunitoshi, the nioiguchi is one level tighter and the interior of the temper tends to appear comparatively quiet, such that the ji and ha convey a character of composed restraint rather than overt strength. Fine kinsuji, sunagashi, and occasional yubashiri provide subtle internal activity, while the boshi typically runs straight or in gentle notare, turning back in ko-maru. Kyoto-style saka-ashi and gyaku-ashi appear in certain works, reinforcing the blades' identity as Kyo-mono. Hisanobu's work stands close to his father's manner, with ko-itame mixed with conspicuous streaks of masame tendency, the same whitish shirake-like utsuri, and a suguha-cho mixing small gunome and slight midare or choji tendencies. Among the group's tanto, which are relatively numerous, some employ kanmuri-otoshi-zukuri construction -- a feature shared with Rai Kunitsugi and considered one of the distinctive characteristics of the broader Rai school.

The Ryokai lineage occupies a position of quiet but considerable importance within the Yamashiro tradition. Its tachi characteristically display the orthodox late-Kamakura silhouette -- slender, graceful forms with pronounced taper, deep wazori curvature, funbari, and ko-kissaki -- conveying a dignity and archaic elegance that the setsumei describe as deeply appealing. The emergence of Hisanobu's signed tachi bearing the name Kurozaemon fundamentally revised scholarly understanding of both father and son, proving that a Juyo Bunkazai-designated tachi previously attributed solely to Ryokai was in fact a collaborative work. Hon'ami appraisals, including origami by Kochu and kinzogan-mei attributed by Koson, attest to the esteem in which Ryokai's work has long been held, and one blade carries a tradition of having been worn by Miyamoto Musashi. At its finest, the Ryokai group's work bears a striking resemblance to Rai Kunitoshi and yet remains sufficiently individual -- in the whitish cast of the jihada, the tight urumi-tinged nioiguchi, and the composed restraint of both ji and ha -- to constitute a recognizable idiom that represents one of the most refined and elegant expressions of the Yamashiro tradition.