Tomokuni is handed down as the son of Kunitoshi and, on one account, the younger brother of Kunizane, which sets him within the second great generation of the Yamashiro school and makes him a near kinsman of Kunimitsu. He is a minor master of that house, and the chief fact of his record is its scarcity. The published sources report no under his name, only a handful of short and small , and even those are few, so that almost the whole of his designated body is carried to him by old appraisal. From what survives the sources read two Tomokuni, an earlier hand in the circle of Kunitoshi and a second working in the period to whom most existing blades are assigned, and they ask whether that second smith is the Tomokuni recorded under the Bunna era of the old sword registers, leaving the question open to further study. He is thus less a documented individual than a name read off a small group of late blades, and the interest of those blades lies in how they part from the rest of the school.
That parting is stated plainly. The published sources say his work differs somewhat from Kunitoshi (来国俊とはやや作風を異にして), the broad, the a standing stronger than is usual among the school's makers, and the temper a -toned in place of the calm that is the hallmark. Every one of his blades carries that notare base mixed with , here and there small , deep in with the well applied, and into the run and , and , with drifting and detached , and burning along the back. The is bright. The shape fixes the period at a glance, a wide, thin, of shallow that the texts read at once as work, with the one piece cut down to a . His is a worked, -laden set on a , and that combination, more than any single feature, is what a Tomokuni blade looks like.
The beneath the temper is what keeps the name. The is an , on the finest a closely packed, with adhering well and on one blade thick, entering and a faint standing on two of them. The steel neither whitens nor sinks as a northern would; it holds the clear, -covered surface of Yamashiro work, and the published sources read the school in it directly. The answers the disturbed , running in as a or, on the broadest blade, sweeping straight with and pointing faintly before a long return, while the small turns close the quieter pieces. The keep the school habit, with and a , and , twin grooves and a cut on these small blades. On each blade the judgment closes in the terms, that the shape shows the period and the and show the school, so that on one the sources find the school's traits present and the Tomokuni attribution sound (来一派の特色があり、来倫国の所伝はよい).
The rarity of his signed work is the spine of the scholarship. Because so little is signed, the published sources build the second-generation reading on style rather than on inscriptions, and the argument turns on the departures that mark his hand. On one they observe that the wide , the unusually strong for the school, and the -toned carry a strain that connects to (一脈信国に通じるものがある), and reason from exactly this difference that a distinct second generation may stand behind the name, perhaps the Bunna-era Tomokuni of the registers. The form keeps to the small end of the range. The two signed pieces and four among the blades are short and , never the the older masters are known by, and the one signed example wears a rather than a chiselled signature. He is, in short, a smith reconstructed by appraisal, the most exactly knowable thing about him being the manner itself.
That manner places him at the school's edge, where the line opens toward the -influenced styles of the day, and his brother stands at the edge. On the broadest blade the published sources turn to Kunizane, handed down as Kunitoshi's pupil or as his son and Tomokuni's elder brother, and note that some of Kunizane's signed work takes on a cast and comes near to Hasebe (皆焼風をおびて長谷部に近似した出来口のもの). Tomokuni's own departure runs the direction without going so far, his stronger and his reaching toward while the holds him to Kyoto. What sets him apart within his own house is therefore positive and grounded in his blades: a that stands where the school's lies flat, a where the school keeps , and a activity of , , and richer than the quiet temper. It is by these, not by any borrowed resemblance, that a wide blade is returned to Tomokuni rather than read past him.
Almost the whole of his record is attributed to him by old appraisal, and his connoisseurship standing reflects a sound but modest hand, rated Jo- with a Toko Taikan valuation in the middle range. A small group of his blades has reached the rank, and beyond them a scatter of works survives only in the research record, two of them held by the Tokyo National Museum and the Kurokawa Research Institute while the rest stay in private hands, with no provenance preserved among them. The published sources single out the best of the pieces for the soundness of both and , calling the broadest an elegantly finished sword without flaw in or (地刃共に破綻のない上品にまとまった優刀である). A Tomokuni is not a National Treasure held forever beyond reach, but neither is it a sword that comes readily to market. The surviving body is small, most of it is held rather than traded, and a signed example is rarer still, so that a private blade by this name is among the less common things a collector of the school could expect to encounter, met with patience rather than sought to order. For a student of how the Yamashiro line bent toward the new manner without leaving its own behind, his few wide, -laden blades are the place where that turn can actually be seen.