SteveM

Here is something in Japanese https://tokka.biz/sword/tadatsuna7.html

服部造　Hattori-zō (made by Hattori)

Shuzan. 秀山 1915 to 1925, apparently. Look towards the bottom of the link. https://gotheborg.com/marks/satsuma.shtml

柳川 would be my guess.

Hello Grey, Asai/Azai is Tadatsuna's own last name, and forms a part of his own signature on some swords. In Nobunaga's time there were several branches of the Asai/Azai, some who didn't face the same fate as the Azai who were persecuted by Nobunaga. Nowadays it is a relatively common last name. Uji means a kind of aristocratic clan name, much the same way that Fujiwara and Tachibana are clan names. Hopefully the above makes sense.

明治天皇御製 我國の為をつくせる人々の名もむさし野にとむる玉かき Poem from His Majesty, Emperor Meiji (roughly) May the souls of those who gave their lives for this country find peace here on the fields of Musashino

You don't see the resemblance?

國 (or 国 in its abbreviated form) has a calligraphic form that is very highly stylized. The stylized form has no box around it. It is one of those calligraphic forms that look absolutely nothing like its normal form, and makes people scratch their heads. https://word.4ndex.com/name/2-1/215-kuni.html Plus, if I'm not mistake there were at least two gunto smiths who used the name Sukekuni. I don't know which one this is. His calligraphic style should give him away.

Looks like 祐国 (Sukekuni). Date is 昭和二十年一月 (January 1945)

Knowing the maker is always good and important, and in this case the maker seems to be a smith of some skill, so I wouldn't say this is insignificant. Also, the unique design on the tang, and even the "good luck" inscription on the reverse side, will all be interesting to collectors. For sure get a new mekugi. Many of us here on the board just whittle down a piece of bamboo chopstick when a new one is needed. (Nobody is a purist regarding the menuki...any piece of bamboo will do as long as it stays in place and holds the sword in). Regarding restoration, for now I wouldn't be in a rush. Just keep it oiled very slightly (so that a film covers the sword, but not enough to allow the oil to collect and pool and potentially drip inside the saya). With Shōwa blades, restoration is always a dicey proposition because the cost of restoration may not be recovered when reselling. I know you are not considering reselling, but it is a data point that someone will eventually consider. I don't know too much about Kanemitsu, but the inscription is unusual enough, that the sword may well be worth spending the couple of thousands of dollars on restoration. Think about this for a while, get some more opinions, show to some collectors or dealers in your area.

Yes - you have it right.

Thanks to @kyushukairu for the reading, but I will happily take the compliment.

I did a quick search in Japanese and came up with a list of possible mon for any family named Kume (久米). This screen grab comes from a book on the Kume family. Its a long list of kamon, and includes a lot of old favorites: plum, bamboo, quince, ginger, cloves, tomoe, lines, etc... There is nothing that shows or ranks the most common mon for the Kume family. https://ameblo.jp/yabutsubakime/entry-12628772032.html

Wakayama lists two Hiroshige artists using these same characters. One is from Mito (real name of Aida), who sometimes also signed as Hiroshige using a different kanji for shige (廣茂). The other is a late Edo artist whose full art name is Seiunsai Hiroshige (青雲斎廣繁) who often used people in his motifs, so this may be the artist who did the work in this thread.

Should be 備州三次住祐秀　　　← Note a very quick search of the internet shows that he usually signed with 備後, but your sword says 備州. I don't know if this is significant for this smith. 慶應三年 Keiō 3 (in calligraphic style of Keiō)