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October 15, 1565 (the date traditionally given for Obu Toramasa's death; Yoshinobu was confined at Tōkō-ji and died in 1567)
Kai Province — Tsutsujigasaki Mansion (Kōfu) and Tōkō-ji
Forces
Takeda Shingen (the head of the house)
Takeda Yoshinobu's side (the heir and his retainers)
About 12 min read
In 1565 (Eiroku 8), Takeda Yoshinobu, eldest son of the Kai daimyo Takeda Shingen, was said to have plotted against his father and was confined at Tōkō-ji in Kōfu. His guardian and tutor Obu Toramasa killed himself in connection with the affair. The page on Obu Toramasa in Kōfu City's "Twenty-Four Generals of Takeda" series gives his date of death as the 15th day of the 10th month of Eiroku 8, and this entry follows it (the date is given as it appears, without conversion to the Gregorian calendar).
Yoshinobu died at Tōkō-ji in 1567. Whether it was illness or suicide is disputed. The incident is understood as bound up with the Takeda succession, the relationship with the Imagawa, and Shingen's shift in diplomatic course.
Yoshinobu is said to have been born in 1538 as Shingen's eldest son, with Shingen's principal wife, Lady Sanjō, as his mother. Shingen took the headship in 1541 by driving out his father Nobutora, and Yoshinobu was raised early as heir.
At his coming of age he received a character from the shogun Ashikaga Yoshiteru and took the name Yoshinobu, a sign that the Takeda, as military governors of Kai, valued ties with the shogunal house. His guardian was Obu Toramasa. Yoshinobu is also said to have fought at the fourth battle of Kawanakajima in 1561, where service in the field helped cement a young heir's standing.
Obu Toramasa was a Kai warrior and senior Takeda retainer, counted among the Twenty-Four Generals. He served the Takeda from Nobutora's time and later supported Shingen. Yamagata Masakage is described as his younger brother (some sources say nephew) and is known to have taken over the Obu name after Toramasa's death. Toramasa's unit is sometimes said to be a source of the Takeda "red armor" tradition, but this includes later lore.
As Yoshinobu's guardian, he oversaw the heir's upbringing, a role that created an especially close bond within the lord-retainer relationship. Yoshinobu's fate was therefore tied closely to Toramasa's.
The usual explanation centers on the changing relationship with the Imagawa. Around 1554 the Takeda, Imagawa, and Hōjō formed the so-called Kō-Sō-Sun alliance. As part of it, Shingen's eldest daughter married Hōjō Ujiyasu's son Ujimasa, and Yoshinobu took a daughter of Imagawa Yoshimoto (later called Reishōin) as his wife. For Yoshinobu, the Imagawa were thus his wife's family and an important hinge of the alliance.
In 1560 at Okehazama, however, Yoshimoto was killed by Oda Nobunaga. His successor Ujizane is said to have lacked his father's command, and the Imagawa weakened quickly. For Shingen the value of the alliance fell, and expansion into Suruga came into view.
Shingen meanwhile drew closer to Nobunaga. In 1565 it was reportedly decided that Nobunaga's adopted daughter (Ryūshōin) would marry Shingen's fourth son Katsuyori, a sign of a turn toward treating the Imagawa as an enemy.
In this setting it would be unsurprising if Yoshinobu, married to an Imagawa daughter, resented his father's new course, which is the commonly told interpretation. As the conflict deepened, retainers who valued ties with the Imagawa are said to have gathered around Yoshinobu.
Contemporary sources are scarce and later chronicles carry much of the account, which generally runs as follows.
In 1565 a movement to install Yoshinobu and remove Shingen was discovered. Shingen punished those said to be involved. Obu Toramasa, regarded as the central figure, was either ordered to kill himself or did so to take responsibility. Other retainers close to Yoshinobu are said to have been punished too, but their number and names differ by source and are not established.
Yoshinobu himself was not executed but confined at Tōkō-ji in Kōfu. Some think Shingen avoided harsh punishment because a father was dealing with his own son, but this remains conjecture.
The incident is variously called the "Yoshinobu Incident" or "Yoshinobu rebellion," and how concrete the "rebellion" actually was remains unclear. Views range from a plot to kill Shingen to a mere dispute over policy.
Yoshinobu is said to have died at Tōkō-ji in the 10th month of 1567, around age thirty by Japanese count, either of illness or by his own hand.
His wife Reishōin stayed in Kai after his confinement but is said to have been sent back to the Imagawa in 1567, a sign that Takeda–Imagawa relations had definitively broken down.
In the 12th month of 1568 Shingen invaded Suruga, and the Kō-Sō-Sun alliance effectively collapsed. In this light the incident is placed as the greatest internal friction at the moment the Takeda changed course from maintaining the Imagawa alliance to invading Suruga.
After Yoshinobu's death, the fourth son Katsuyori became heir. Katsuyori had been destined to carry on the Suwa name, but Yoshinobu's fall brought him the Takeda succession. Even after becoming head, he is also said to have struggled to control the retainer band.
Whether the incident led directly to the Takeda's fall in 1582 is debated. Some see the turmoil of succession as casting a shadow on retainer unity, while the more usual view is that the fall resulted from several factors, including military exhaustion after Nagashino (1575) and the Oda–Tokugawa offensive. This entry avoids a firm judgment.
Within the scope of the source used, no reliable record links a particular famous sword directly to this incident. In terms of swords, one can note only that seppuku was one accepted way for a warrior to take responsibility, but that was a general custom of the time and not specific to this incident.
The "red armor" is sometimes mentioned in connection with Toramasa's unit, but the anecdotes mostly concern Yamagata Masakage's unit, and no surviving weapons or swords personally used by Toramasa can be confirmed. This entry therefore does not go into the swords themselves and aims at understanding the Takeda's historical background.
The incident is often taken as an example of how serious a conflict between heir and lord could become within a daimyo house. It also shows how one event, the battle of Okehazama, reached through changing alliances to the fate of a house far away in Kai.
Today Tōkō-ji in Kōfu holds Yoshinobu's grave, and Obu Toramasa is honored as one of the Twenty-Four Generals. The site of Tsutsujigasaki Mansion has been preserved as Takeda Shrine and conveys the center of Kai in the Sengoku period.