Photo/IllutrationA letter by Akechi Mitsuhide addressed to Tsuchibashi Shigeharu (Provided by the Minokamo City Museum)

TSU--An original letter handwritten by Akechi Mitsuhide (1528-1582) days after he turned against his lord, Oda Nobunaga (1534-1582), has been discovered.

The original letter was folded many times at intervals of 2 centimeters, indicating it was a confidential document.

Tatsuo Fujita, a professor of Japanese history at Mie University, concluded the signature on the letter was that of Mitsuhide.

Fujita said Sept. 11 that the letter was likely addressed to a warlord in central Japan, and that the missive was probably carried with great care after being folded into such a small piece.

A copy of the contents of the letter was previously discovered, but confirmation that the missive was definitely written by Mitsuhide would be of historical importance.

The letter measures 11.5 centimeters by 56.7 cm and is owned by the Minokamo City Museum in Gifu Prefecture.

It was addressed to Tsuchibashi Shigeharu in the Kishu region of central Japan, 10 days after Nobunaga’s death, known as the Honnoji Incident, on June 2, 1582.

Tsuchibashi is believed to have been the leader of samurai who rose up against Nobunaga in Kishu, the area now known as Wakayama Prefecture.

The letter says Mitsuhide agreed to a plan to allow Ashikaga Yoshiaki (1537-1597), the last shogun of the Ashikaga Shogunate, to return to Kyoto, although Yoshiaki had formerly been driven out of the city by Nobunaga.

In the document, Mitsuhide writes, “I agree to the idea of his returning to Kyoto,” as Tsuchibashi sided with Yoshiaki.

Although the shogun’s name does not appear in the letter, the words used to refer to people of high rank, such as “joi” (a nobleman’s wishes) and “gojuraku” (a nobleman entering Kyoto), are used in it.

“Those expressions should be used for no one but Yoshiaki after Nobunaga died,” Fujita said.

There are various theories as to why Mitsuhide betrayed Nobunaga.

“The letter clearly shows Mitsuhide staged a coup under his political plan to reconstruct the Ashikaga Shogunate by honoring Yoshiaki,” Fujita argued.