Nobody

So no kurikara (草の倶利伽羅) by Gassan Sadakazu 1st

Maybe 後 - back/behind/after.

美濃国貞正鍛之 – Sadamasa in Mino province forged this.

i suspect that it may be such a document and was written after Meiji era.

That is another Showa. The paper says late Showa: 昭和 (1926 - 1989).

1. Wakizashi Mumei: Thought to be 宗弘 (Munehiro) in Fukuoka (福岡) Late Showa era 2. Katana Mumei: Thoght to be Kanemoto (兼元) in Noshu (濃州) Circa Tensho (天正, 1573-1592)

I know I am late, but I still do not understand the paper. The paper looks an incorrect explanatory note rather than a certificate. There are several points I cannot understand. The paper says that the armor maker Myochin Muneyoshi (明珍宗吉) was invited to Shonai by Sakai Saemon no jo Tadatsugu (酒井左衛門丞忠次), and Tadatsugu was the 27th Lord of the Shonai domain. However; 1. Sakai Tadatsugu (酒井忠次) died in 1596 before the Shonai domein was established. Ref. Sakai Tadatsugu - Wikipedia 2. The first Lord of the Shonai domain is Sakai Tadakatsu (酒井忠勝), who is the grandchild of Tadatsugu. 3. The last Lord of the Shonai domain is Sakai Tadamichi (酒井忠宝) and he is 12th load. So, there is no 27th Load of the Shonai domain. 4. If Myochin Muneyoshi made the armor in late Edo period, what about the first part of the paper?

兼継 - Kanetsugu

高崎三郎金繁 - Takasaki Saburo Kaneshige Ref.

兼常 - Kanetsune

Your paper is not NBTHK’s paper, though it imitates the style of NBTHK. It was issued by 美術日本刀保存審査會 (Bijutsu Nihonto Hozon Shinsakai) in 1974.

関藤井兼音作 – Seki Fujii Kaneoto saku

関正行 - Seki, Masayuki

則光 - Norimitsu

亰都藤原安廣 - Kyoto Fujiwara Yasuhiro

I agree with your reading for the mei. 関住人各務行直作 – Seki junin Kagami/Kagamu Yukinao saku One kanji on the back side might be 弟 – younger brother. I am not sure.

The description on the Torokusho is “なし（傳）粟田口 – None, (Thought to be) Awataguchi”. なし(Nashi) means Mumei in this case. Basically, registration papers do not mention any attribution. The Torokusho of your katana was issued in the first year when the registration system started. So, there might be a little confusions.

Everything can be a motif such as fisherman’s net.

This is just a shot in the dark. 畚 (mokko) – a straw basket [for carrying earth]

濃刕関住人源天秀謹作之 – Resident in Noshu Seki, Amahide respectfully made this. 皇紀二千六百年拾月日 – 2600 Imperial year (1940), 10th month

New characters for 日刀保 look like low resolution fonts similar to 16 dot font on VGA monitors in 1990s.

I have this TH paper dated December 15, 2023. There are 日, 刀, and 保 marks as previous papers. However, each mark is not clearer than marks on privious papers. The each caracter now consists of small red dots and does not look fine.

重幸 - Shigeyuki

小松﨑納 – Komatsuzaki supplied. I guess that 小松﨑 (Komatsuzaki) is 小松埼茂助 (Komatsuzaki Mosuke) and was the president of 壽屋 (Suya Shoten). Ref. 小松崎茂助 (8th Edition) - JINJIKOSHINROKU (who's who) Database (nagoya-u.ac.jp) FYI; Suya story - Military Swords of Japan - Nihonto Message Board (militaria.co.za)

I think that the 2nd line means the polisher’s name. 研上 – Polished 譲之謹 – Noriyuki/Masayuki (or other readings) respectfully