A signed in Honma's inventory of the Imperial collection, now held by the Tokyo National Museum, is the one fixed point in the record of Tomokuni. He is handed down as the son of Kunitoshi and, on one account, the younger brother of Kunizane, which places him in the second generation of the Yamashiro school and makes him a near kinsman of Kunimitsu. His signed work is rare in the extreme. One paper states that his signature is very seldom met, that there is no , and that only a few are seen. Almost the whole of his designated body is therefore , carried to him by old appraisal, and from it the published sources read two smiths of the name: a first generation, the pupil of Kunitoshi, and a second working in the period.
The hand is the one most often met, and the published sources describe it as a departure from the school. His work differs somewhat from Kunitoshi: the is broad, the a standing stronger than is usual among the makers, and the a -toned in place of the calm that is the hallmark. Each of his blades carries a base mixed with , at times with , deep in and with the well applied. and enter, and run through the , and on a few blades and are added, both rare across the school. The shape fixes the period, a wide, thin, of shallow , with one blade cut down to a .
Beneath the temper lies the that holds the name. The is an , on one a compact , the adhering well and on one blade thickly; enter, and a faint stands on two of the blades. On one the grain mixes and stands out. The answers the disturbed , running in as a , or on the blade sweeping straight with and pointing faintly before a long return, while other pieces turn back in a . The include , a , a with , and . On each blade the judgment closes in the same terms: the shape shows the period, the and show the school, and the attribution stands, so that one paper finds the school's traits present and the Tomokuni attribution sound.
The signed stands apart. It is a of about eight , almost without and of ordinary width, forged in a well-packed with and . The is a with and , and , well applied, and a above the ; the runs in as a with , and a is cut on both faces. Its commentary records that only this and one other signed piece have been seen, and that unlike the Tomokuni of the attributions it is small and ordinary and appears to be late work. The Tomokuni handed down as Kunitoshi's pupil would then be the maker of work like this, and the attributions, all judged , a second generation. The papers reach toward the same second smith from the other side, asking whether he is the Tomokuni recorded under the Bunna era in the old registers, and leave the matter to further study.
Both hands lean away from the quiet Kunitoshi manner. The commentary calls the signed an exceedingly good reference piece, its distinctly stronger and its temper more disturbed than Kunitoshi's, and finds in that quality something in common with Kunimitsu. For the work a paper finds a strain that connects to , and reasons from this difference that a distinct second generation may stand behind the name. The same body of work draws in his brother. On the the published sources turn to Kunizane, and note that some of his signed work takes on a cast and comes near to Hasebe. What sets Tomokuni apart within his own house is grounded in his blades: a that stands, a where the school keeps , and and added to the .
Fujishiro rates him Jo . Five of his blades have been designated , one of them a and the other four , and none has reached . No National Treasure or Important Cultural Property stands under his name, and no provenance is preserved among his recorded blades. The published sources single out the as an elegantly finished sword without flaw in or . With the signed in a public collection and the surviving body so small, a Tomokuni does not come readily to market. Most of what exists is held rather than traded, a chiselled signature is rarer still, and a privately held example of recorded whereabouts is among the less common things a collector of the school could expect to encounter, met with patience rather than sought to order.