Choen was a swordsmith of Buzen Province, traditionally said to have been active around the Eien era (987-989). According to the , several smiths bearing this name are known across succeeding generations, and those using a two-character signature are associated with the Genryaku era (1184-1185). There is also a tradition identifying Choen as a Yamato smith. Signed works are extremely few, making attribution a matter of careful stylistic appraisal rather than documentary certainty.
The characteristics attributed to Choen's work include a conspicuously sticky, quality in the , with fine adhering closely. The forging is a well-compacted with areas tending toward , producing an attractive, somewhat whitish cast overall. The ranges from fine to with , and within it places showing an (moist, soft) tendency appear -- features that, as the notes, "well express the characteristics of Kyushu work." The presence of , , and further enriches the temper. These qualities strongly call to mind works such as those of Bungo Yukihira, and the period of the oldest surviving example should not descend later than Yukihira's own time.
Blades attributed to Choen display an archaic with slender proportions, , and deep -zori, in which "both and are outstanding." One blade preserves an in bold, thick chisel-work -- the oldest surviving signed example known today. A further notable tradition holds that the ancient treasure sword of the Minamoto clan, the called Usumidori ("Pale Green"), is in fact this very blade. Even where attribution to Choen cannot be confirmed with certainty, as with a bearing a Kenpo 1 (1213) date inscription, the workmanship and inscriptions remain valuable.