Shima Sakon: New Letter Found, Who Was Mitsunari's General?

On 26 September 2026, NHK reported that a copy of a letter had been found that the samurai Shima Sakon wrote while in the service of Hashiba Hideyoshi. In it he urged the temple Kongōbuji on the sacred Mount Kōya to follow Hideyoshi. An expert called the document "extremely valuable" because it sheds light on Sakon's political career, which is full of riddles.

That is remarkable, because Sakon is among the most famous generals of the Sengoku period. He appears in video games like "Nioh" and "Onimusha: Dawn of Dreams," he is said to have advised Ishida Mitsunari and to have fallen at the Battle of Sekigahara. In short: hardly any samurai has so much legend in circulation and so little reliably documented. The sources contradict each other on almost every date.

Shima Sakon was actually called Shima Kiyooki, other names are Shima Tomoyuki and Shima Katsutake. According to the usual account, he was born on 9 June 1540 in Heguri in Yamato Province, today's Nara Prefecture. He served first the Hatakeyama clan and then Tsutsui Junkei, in whose household he rose to head of the retainers. Together with Matsukura Shigenobu he was called "Sakon" and "Ukon," "left" and "right," the two hands of the clan.

After Junkei's death in 1584, Sakon became masterless, a rōnin. Then came the most famous story: Ishida Mitsunari, Hideyoshi's administrator, is said to have offered him half of his own income, 20,000 of 40,000 koku. A koku was the amount of rice that feeds one person for a year. The tale shows how highly Mitsunari valued the fighter, and it is told gladly because it paints Mitsunari as a man without greed.

Even the point at which Sakon came to Mitsunari is unclear. One account gives January 1586. Another holds that he began working for Mitsunari after the death of Toyotomi Hidenaga in 1591. A third says that after the death of Hideyasu, Hidenaga's son, in 1594, Sakon became masterless again and Mitsunari then recruited him. A fourth account gives 1598. The numbers are uncertain too: according to one source, the Tsutsui paid the Shima house a total of 15,000 koku, less than the 20,000 Mitsunari is said to have offered.

Even Sakon's death is not clear. According to the common accounts, he died on 21 October 1600, the day of Sekigahara. Another account says he died of his wounds about a month after the battle, and a third that it is unknown whether he survived the battlefield. What is certain is little: he was a known fighter, he served various lords, and by 1600 at the latest he stood on Mitsunari's side.

The NHK report is short: what was found is a copy of a letter in which Sakon, as a retainer of Hashiba Hideyoshi, calls on the temple Kongōbuji to follow Hideyoshi. An expert says the document shows Sakon's political movements, which are otherwise unknown. Details such as date and wording are not given in the brief report.

A specialist blog that cites the investigation adds that the copy comes from a collection of old documents held by the National Institute of Japanese Literature and was discovered by a historian at the Historiographical Institute of the University of Tokyo. The letter dates to the period immediately after the Battle of Shizugatake in 1583, in which Hideyoshi defeated his rival Shibata Katsuie. It is to appear at the end of fiscal year 2026 in the source collection Dai Nihon Shiryo, and so far only three letters by Sakon were known. These details come from a blog and not from NHK, so they must be confirmed by the scholarly publication.

Why is a letter to a temple political? Mount Kōya was more than a monastery: it owned land and kept armed monks. In 1585, Hideyoshi attacked the temples Negoro-ji and Kokawa-dera and in April 1585 called on Mount Kōya to submit under five conditions. One of the monks, Mokujiki Ōgo, mediated, and Kongōbuji accepted the conditions at once.

In June 1585, Hideyoshi issued a document with a red seal: he returned land in the districts of Uchi in Yamato and Ito in Kii worth 3,000 koku and donated 10,000 koku for the repose of the soul of his mother, the Ōmandokoro, with which the Golden Hall of Kongōbuji was rebuilt. According to one account, Hideyoshi stood before the mountain with 100,000 men. A letter from Sakon pressing the temple to obey fits this time of negotiations, but according to NHK, the exact dating of the letter is not known.

After Hideyoshi's death in 1598, the quarrel broke out. After the death of Maeda Toshiie, seven generals planned to kill Mitsunari, he fled with Sakon and others to the house of Satake Yoshinobu. At Sekigahara in 1600, Sakon according to Wikipedia commanded a unit of about 1,000 men, some sources say he led musketeers. According to tradition he advised a night attack that was ignored, but that comes from compilations and not from a letter. He was hit by riflemen led by Kuroda Nagamasa.

Everything after that is legend, and it is large: the general did not return, and nobody knows for certain whether he fell on the field or died of his wounds. Perhaps that explains why a single new letter gets so much attention. It is a piece of secured life in a biography made mostly of stories.

Whoever knows Sakon knows him mostly from video games. In "Nioh" he appears as a character, in "Onimusha: Dawn of Dreams" as a recurring opponent, and both games retell his story by the legend: the fighter who served for half his lord's income. The games stick to tradition, not to the sources, and with a man about whom the sources give so little, that is probably not possible any other way.

That is exactly why a new letter matters. It can't replace the legend, but it shows that the story behind the name consisted of real people and real letters, which only gradually resurface.

To wrap up, the short version, so fact and story don't blur.

Sakon shows how thin the sources behind a famous figure can be. That's why every season in HistoryBytes is split into five categories, and this story touches all five: Shima Sakon as a person, Mount Kōya as a place, the Battle of Sekigahara on 21 October 1600 as an event, a retainer's loyalty as an idea, the newly found letter as an object. That's how the Whispers of the Samurai season builds the whole picture of a world in which legend and source can hardly be told apart.

Whether Sakon really received the half-income offer, whether he fell at Sekigahara, whether he was born on 9 June 1540 at all, we don't know for certain. What we have more of since September 2026 is a letter he wrote as a retainer of Hideyoshi. It is short, it is a copy, and it is still more than was previously known from his hand. For lovers of history that is a nice thought: even about the most famous warriors of the Sengoku period, an archive can still hold something new.