Choen was a swordsmith of Buzen Province, traditionally said to have been active around the Eien era (987-989). According to the meikan, 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, nettori quality in the jigane, with fine ji-nie adhering closely. The forging is a well-compacted ko-itame with areas tending toward masame, producing an attractive, somewhat whitish cast overall. The hamon ranges from fine suguha to chu-suguha with gunome, and within it places showing an urumi (moist, soft) tendency appear -- features that, as the NBTHK notes, "well express the characteristics of Kyushu work." The presence of ko-nie, kinsuji, and sunagashi 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 sugata with slender proportions, ko-kissaki, and deep koshi-zori, in which "both ji and ha are outstanding." One blade preserves an orikaeshi-mei 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 tachi called Usumidori ("Pale Green"), is in fact this very blade. Even where attribution to Choen cannot be confirmed with certainty, as with a tanto bearing a Kenpo 1 (1213) date inscription, the workmanship and inscriptions remain valuable.