Obu Toramasa served as a bushō during the Sengoku period.  He was a senior retainer of the Kai-Takeda clan.

From the era of Takeda Nobutora, Toramasa served as a hereditary chief retainer of the Takeda family.  He resided in Uchiyama Castle in the Saku District of Shinano Province.  After the ouster of Nobutora, Toramasa served his eldest son, Takeda Shingen.  Deeply trusted by Shingen, he served as a mentor for Shingen’s eldest son and designated heir, Takeda Yoshinobu, and was the head of the Red Corps, the vanguard forces of the Takeda.  However, owing to complicity in a rebellion by Yoshinobu known as the Yoshinobu Incident, Toramasa was compelled to commit seppuku.  While he is referred to as Toramasa, that name does not appear in a record signed by close associates of Yoshinobu so his real name remains uncertain.

Service to Takeda Nobutora

The Obu were members of the Kai-Genji, descended from Obu Tadamune, the son of Minamoto no Yoshitada who was the fourth son of Minamoto no Yoshiie of the late Heian period.  There is also a theory that the clan descended from the Ou clan of ancient times.  In Kai Province during the Sengoku period, Obu Dōetsu was a retainer of Takeda Nobutora.  On 10/17 of Eishō 12 (1515), Dōetsu, along with Genshirō (who appeared to be his son) died in battle against Ōi Nobusato, a kokujin, or provincial landowner, from Nishigōri.  Obu Genshirō appears to have been the father of Toramasa and Yamagata Masakage.

Toramasa is surmised to have been born in 1504, but his year of birth is not certain.  He is said to have been born in the village of Obu.

In 1531, Toramasa joined Imai Nobumoto and Kurihara Nobutomo to rebel against Nobutora, but was defeated and surrendered.  After being pardoned, he entered service for Nobutora.  In 1536, after Hōjō Ujitsuna invaded Suruga Province, Toramasa joined Nobutora to participate as reinforcements for the Imagawa army and achieve a significant victory over the Hōjō army.  In 1538, he fought against the allied forces of Suwa Yorimitsu and Murakami Yoshikiyo.  Despite having only a small contingent, he defeated his opponents who enjoyed numerical superiority, and Toramasa himself captured ninety-seven enemy heads.

In 1541, Toramasu, along with Itagaki Nobukata and Amari Torayasu who were powerful kokujin and veterans of the Takeda family, backed Nobutora’s eldest son and designated heir, Takeda Harunobu (later known as Takeda Shingen), ousted Nobutora to Suruga Province, and, thereafter, supported Harunobu as veterans of the Takeda family.

Service to Takeda Shingen

In 1548, after Itagaki Nobukata and Amari Torayasu were killed in action at the Battle of Uedahara, Toramasa became the mainstay of the Takeda forces in support of Shingen.

In military engagements, Toramasa always stood at the front.  In 1553, Toramasa was surrounded at Uchiyama Castle by 8,000 besieging forces led by Nagao Kagetora (later known as Uesugi Kenshin) and Murakami Yoshikiyo.  Nevertheless, Toramasa repelled them with a garrison of only 8,000 men.  In 1561, at the Fourth Battle of Kawanakajima, he served as the commander-in-chief of a detached unit for an assault on Mount Saijo.  Toramasa worked vigorously to advance the interests of the Takeda clan and was appointed to be the mentor (guardian) of Shingen’s eldest son, Yoshinobu, carrying the responsibility as the leading veteran of the Takeda clan.

Latter years

Shingen did not have a good relationship with his son, Yoshinobu.  The conflict between them deepened over their policies toward the Imagawa clan of neighboring Suruga Province.  Toramasa was then apprehended for supporting Yoshinobu in the plotting of a rebellion.  Taking responsibility of the plot, he committed seppuku.  According to records at the Seikei monastery on Mount Kōya, this occurred on 10/15 of Eiroku 8 (1565).  Under an alternate theory, it occurred sometime between the ninth to tenth months of 1565.  In any event, he was sixty-two years old.

The Obu family came to an end and the band of retainers was taken over by his younger brother, Saburō Hyōe-no-jō, who adopted the surname of Yamagata.

Toramasa had a son named Obu Masatoki, and, after the Yoshinobu Incident, he turned for support to the Sanjō, a family of nobles with whom he had a connection, and adopted the surname of Koya.

In the ninth month of 1553, during the First Battle of Kawanakajima, Obu Sakyō-no-jō was dispatched to support the defenders of Kariyahara Castle in Shinano which was under attack by the Nagao clan.  He is deemed to be a successor of Obu Fujikura who eliminated the Tōjō clan in 1551 and the son of Toramasa.  The name of Obu Sakyō-no-jō appears as another kunishū in records from 1559 of landowners of the Odawara group of the Gohōjō clan of Sagami Province.

There are various theories regarding the reasons for Toramasa to take his own life.  Under one view, Toramasa devised the plot himself so he could communicate it to Saburō Hyōe-no-jō, and, to protect Yoshinobu, he was found guilty of being the ringleader.  Under another view, Toramasa frequently opposed Shingen’s ruling policies in Shinano and frequent conflicts with Uesugi Kenshin.  Or, he wielded significant power within the Takeda family so the Yoshinobu Incident provided an opportunity for Shingen to purge Toramasa.  Similar to Toramasa, Anayama Nobuyoshi (the younger brother of Anayama Nobutada) was also found complicit in the event and committed seppuku.

Character

As a veteran among veterans, Toramasa served two generations of the Takeda family, namely, Takeda Nobutora and Takeda Shingen.  An intrepid bushō, he was called the “fierce tiger from Mount Kabuto.”  He struck fear in his enemies and was counted among the Twenty-Four Generals of the Takeda.

All of the members of his battalion were adorned in red-colored armor and were widely known as the Red Corps vanguard forces of the Takeda.  These forces represented the elite military corps of the Takeda army.  Later, the Red Corps was emulated by Toramasa’s younger brother (Yamagata Masakage), Ii Naomasa, and Sanada Nobushige (Yukimura).