昭平刀匠は、本名を宮入堅一といい、大正2年長野県に生まれ、昭和12年栗原彦三郎の日本刀鍛錬伝習所に入門、新作日本刀展覧会、陸軍軍刀展で多くの賞を受賞。昭和27年、師栗原彦三郎の呼びかけに応じ、サンフランシスコ講和条約記念刀を制作する。昭和28年美術刀剣の作刀が可能になり文化財保護委員会より製作承認を受ける。昭和30年より昭和34年まで日本美術刀剣保存協会の作刀技術発表会で特賞を受賞、昭和35年無鑑査。昭和38年に重要無形文化財保持者（人間国宝）に認定される。昭和48年｢昭平｣を｢行平｣と改める。昭和52年64歳で没。この刀は、身幅広く、反りやや深く、先幅も広く、大鋒となる南北朝の体配で、つんだ板目肌に、杢目肌・小杢目肌交じり、地沸厚くつき、地景細かく頻りに入る古作を思わせる精良な地鉄に、小のたれに、小互の目交え、小足頻りに入り、匂口も柔らかく、匂口明るい。兼光写しの傑作である。Shohei swordsmith, whose real name is Kenichi Miyairi, was born in Nagano Prefecture in 1923. He entered Hikosaburo Kurihara's Japanese sword training training school in 1937 and won many awards at the New Japanese Sword Exhibition and the Army Gunto Exhibition. In 1952, at the request of his teacher Hikosaburo Kurihara, he produced a peace memorial sword. In 1953, he became able to create art swords and received production approval from the Cultural Properties Protection Committee. From 1955 to 1959, he received a special prize at the Japan Art Swords Preservation Association's sword-making technology presentation, and in 1960 he was unexamined. In 1963, he was certified as an Important Intangible Cultural Property Holder (Living National Treasure). In 1973, "Shohei" was changed to "Yukihira." Died in 1977 at the age of 64.
This sword has wide Mihaba, Slightly deep Sori, Big Sakihaba, The Nanboku-cho style of Oh-Kissaki is evident. Tsunda-Itamehada, Mokumehada, Mixed Small-Mokumehada, Jinie entered thick, Chikei entered fine and frequently, The exquisite Jigane is reminiscent of an ancient work, Small-Notare, Mixed Samll-Gunome, Small-Ashi entered frequently, Nioikuchi is soft and bright, This is a masterpiece of Kanemitsu copying.