Let´s stay at the turmoils of the early Nanbokuchō period. In the third month of Kenmu three (建武, 1336), four months after the battle at the Hakone pass, Ashikaga Takauji was stuck on Kyūshū. To this place he was driven by Nitta Yoshisada and Kusunoki Masashige after entering Kyōto, losing the capital just after a short time. The some thousand men of Takauji met the superior army of the Godaigo alliance at the back of Tatara (多々良浜, Hakata Bay, present-day Fukuoka Prefecture), at the same place where once the Mongols arrived. The emperor-loyal alliance was led by Kikuchi Takeshige´s (菊池武重, 1307-1338) younger brother (菊池武時, ?-1341), followed among others by Aso Korezumi (阿蘇惟澄, 1309-1364), the then head of the Aso family. The Aso were as the Kikuchi loyal to the emperor since oldest times.
Right at the beginning of the fightings, the alliance was able to disturb Takauji´s battle formation and split the army. For a moment, it seemed that victory was theirs. But then, a force north wind sprang up and covered Taketoki´s warriors in a huge sand cloud, robbing completely their sight. In addition, many men went over to the ebeny, and this was the disastrous end for the alliance and the victory for Takauji. Takauji was able to use this „tactic of conversion“ because except of the Kikuchi and Aso, most other members of the rather loose alliance held a wait-and-see policy and where not all for Godaigo´s plans. Aso Korezumi – his older brother Korenao (惟直) died in this battle – was able to return wounded to his lands at the foot of Mt. Aso of the same name. His ō-dachi by Rai Kunitoshi (来国俊) with a blade length of more than one meter suffered strongly from the mowing movements Korezumi faced his enemies. Totally exhausted he lied down and was fast asleep, having a strangle dream. A swam fireflies (hotaru, 蛍) – very atypical for this time of the year – came flying along, sitting down on the blade of his Rai Kunitoshi. The entire sword glowed in the dark of the night. Korezumi slept deeply until next morning. Surprised about the dream he immediately unsheathed his sword, but he couldn´t believe his eyes: all chips and cuts of the cutting edge (so-called ha-kobore, 刃毀れ) were gone! As head of the Aso family, Korezumi held also the office of high-priest (daigūshi, 大宮司) of the Aso Shrine (Aso-jinja, 阿蘇神社, present-day Kumamoto Prefecture), and so the sword was kept there as family treasure over generations under the name Hotarumaru (蛍丸).
In 1931, the Hotarumaru was submitted by baron Aso Tsunemaru (阿蘇恒丸), the then head of the family, to the Ministry of Cultural Affairs and was designated as national treasure. After the end of World War II, the sword was lost in the course of the sword hunt of the occupying forces. There are rumours that the blade is still in a unknown private collection in Japan but it is more likely that it was destroyed just like many thousand other swords.
Fortunately we have a drawing of the blade (see picture 28). It was published in the Shūko Jisshu (集古十種), a 85-volume catalogue over ten categories (jisshu, 十種) of antiques (shūko, 集古), commissioned in the twelfth year of Kansei (寛政, 1800) by Matsudaira Sadanobu (松平定信, 1759-1829), the then daimyō of Shirakawa.
The notes at the side of the picture read:
“Higo no kuni, Aso-daigūshi Korezumi Hotarumaru-tachi no zu” (肥後国阿蘇大宮司惟純螢丸太刀圖), “Picture of the tachi Hotarumaru of the Aso high-priest Korezumi from Higo province” (Note: Here, a different character for “sumi/zumi” was used; → compare 澄 and 純).
“Sōchō 4 shaku 5 sun – haba 1 shaku 2 bu – nagasa 6 sun 8 bu” (惣長四尺五寸 幅一寸三歩 長六寸八歩), “Entire length ~ 136.6 cm (the blade length measures 101.3 cm), blade width ~ 3.9 cm, length of the (smaller) hi ~ 20.6 cm”
“Einin gonen sangatsu-ichinichi” (永仁五年三月一日), “first day of the third month Einin five (1297)”
In this context, I would like to introduce another blade by Rai Kunitoshi which is designated as national treasure too. Except of the blade length, it has a very similar shape (sugata, 姿) as the Hotarumaru. This sword is signed with Kunitoshi´s civilian name Magotarō (in the form “Rai Magotarō saku,” 来孫太郎作) and bears the date “Shōō gonen mizunoe-tatsu hachigatsu jūsannichi” (正応五年壬辰 八月十三日, “13th day of the eighth month Shōō five , year of the dragon”). So it was forged just five years before the Hotarumaru. The elegant sugata, the hi which is cutted centrally on the shinogi-ji running through the entore tang and its end before the kissaki, as well as the smaller hi towards the base of the blade – all those elements are identical on both blades.
The smith Kunitoshi belonged to the Rai school in Yamashiro province. Traditionally, he is dated to the Kōan period (弘安, 1278-1288). There are works extant which are signed either with Rai Kunitoshi or just with Kunitoshi, and because these blades are somewhat different in workmanship and shape, it is unclear if there were two generations Kunitoshi.
Picture top: Drawing of the Shūko Jisshu, bottom (not true to scale and vertically mirrored): kokuhō tachi, mei: “Rai Magotarō saku – [kaō] Shōō gonen mizunoe-tatsu hachigatsu jūsannichi,” nagasa 77.3 cm, sori 3.9 cm, shinogi-zukuri, iori-mune, deep sori, funbari, ubu-nakago (in the possession of the Tokugawa Museum, Nagoya)