Nobody

東海道清水住人、盛重作 – A resident of Tokaido Shimizu, Morishige made. 応好 柳雅堂氏 – Responding to the order from Mr. Yanagi Gado 家運長久 – Good future for the family 昭和六十乙丑年八月日 – Showa 60 Kinoto-Ushi year (1985), 8th month

美乗 – Yoshinori/Mijo (reading?)

I cannot read the body of the letter either. The address and the name of the addressee are 市内目黒区向原町二五〇 – In Tokyo, Meguro-ku, Mukaiharamachi 250 山田耕三 殿 – Mr. Yamada Kozo

波平行充 – Naminohira Yukimitsu 瀬戸口長道 – Setoguchi Nagamichi

源任功鍛之 – Minamoto Yoshikatsu forged this. I do not know the correct reading for 任功. There are other readings, and Yoshikatsu is one possibility.

Ref.

I agree with Jussi. The mei looks to be 談議所西蓮 – Dangisho Sairen, and only the last four kanji are in the picture. However, slightly different kanji are used in the mei. (談)儀㪽西蓮

尾州住延舎 – Bishu (Owari province) ju Nobuie

The mei and the stamp on the box are Shogetsu (祥月). Though I know nothing about ceramics, is the mizusashi really Madarakaratsu?

So, the box does not seem to belong to the mizusashi.

斑唐津 - Madarakaratsu 水指 - Mizusashi 祥月造 – Shogetsu made. 宗和 – Sowa

Ref. Vaiśravaṇa - Wikipedia

鐔 - Tsuba 七宝紋所之図 – Shippo, mondokoro no zu (figure of family crests) 朧銀磨地 – Oborogin, migakiji 七宝紋散 – Shippo mon chirashi 金覆輪 珍品也 – Kin fukurin, rare item 無銘 平田彦四郎 – Mumei, Hirata Hikoshiro (attribution) 昭和壬子年秋吉日 – Showa Mizunoe-Ne year (1972), autumn, a lucky day 寒山誌 – Kanzan wrote.

但州 - Tanshu

The name on the nakago is 兼氏 - Kaneuji.

The last character may be 左 (sa/hidari) - left.

“岩船郡八幡村大字八□□ – Iwafune-gun, Yawata-mura, Oaza …” is an old address, and the details are unknown. The address is now included in the following area. Ref. Sanpoku, Niigata - Wikipedia Tohashi – family name Hisajiro - first name I am sure he is no longer living. I do not think that sending it back to Japan is a good idea, unless the blade is national treasure level.

岩船郡八幡村大字八□□ – Iwafune-gun, Yawata-mura, Oaza … 富樫久治郎 – Togashi Hisajiro

紙和鋼安来以吉久作之 – From 紙和鋼 of Yasuki/Yasugi, Yoshihisa made this. I am not sure about the correct reading of 紙和鋼. “和鋼 (wako)” might be another general name of Tamahagane. Ref. 和鋼 - Wikipedia

天明六丙午歳初春 – Tenmei 6 Hinoe-Uma year (1786), early spring 源應擧寫 – Minamoto Okyo’s painting Ref. Maruyama Ōkyo - Wikipedia

I guess that 山本淸 (Yamamoto Kiyoshi, 1883-1960) is the Yamamoto Gonbe’s oldest son. Yamamoto Kiyoshi was a naval officer, politician, and nobility. His father Yamamoto Gonbe (山本権兵衛) was an admiral of the Navy. Ref. 山本清 (海軍軍人) - Wikipedia Ref. Yamamoto Gonnohyōe - Wikipedia Yamamoto Kiyoshi was living in Shiba-ku, Takanawadai-machi in early Showa period. I guess that the card was used before or during WWII. The first three characters of the handwriting might be 外務省 (the Foreign Ministry).

I think that the number written over nine is eight.

The sword is a Chinese reproduction. 中國大連陳朝波 – China Dalian, Chen Chao-Po 辛己年 – Year of the Snake (2001) Ref. Paul Chen sword inscriptions - Auctions and Online Sales or Sellers - Nihonto Message Board

He died in the Battle of Ichi-no-Tani.[5][6] His body was identified by a signed poem that was fastened to his quiver. The poem read:[4]: 96  Evening drawing on, I'll take lodging in the shade of this tree, and make its blossoms my host for the night. Ref. Taira no Tadanori - Wikipedia

Its mei is 関兼延 - Seki Kanenobu.