Kasuga Toratsuna


Kasuga Clan

Kai Province

Kasuga Toratsuna

Lifespan:  Daiei 7 (1527) to 5/7 of Tenshō 6 (1578)

Name Changes:  Kasuga Toratsuna, Kōsaka Toratsuna

Other Names:  Masanobu, Masatada, Harumasa, Haruhisa; [Common]  Gengorō, Danjō-no-jō; [Nickname] Nige-danjō 

Rank:  bushō

Title:  Inspector of the Board of Censors

Clan:  Kasuga, Kōsaka

Lord:  Takeda Shingen → Takeda Katsuyori

Father:  Kasuga Ōsumi

Adoptive Father:  Kōsaka Muneshige

Siblings: 熊麿, Toratsuna

Wife: [Formal] Daughter of Kōsaka Muneshige

Children:  Kōsaka Masazumi (Gengorō), Kōsaka Masamoto (Genjirō), Kōsaka Masasada (Genzaburō)

Kasuga Toratsuna served as a bushō during the Sengoku period.  Toratsuna was a hereditary chief retainer of the Kai-Takeda clan serving Takeda Harunobu (Shingen) and Takeda Katsuyori.  He is included among the Twenty-Four Generals of the Takeda.

Origins of surname

Kasuga Toratsuna is commonly known under the name of Kōsaka Masanobu, but the longest period during which he used the Kōsaka surname was from Kōji 2 (1556) to the ninth month of Eiroku 9 (1566).  He adopted the Kōsaka surname after inheriting the headship to the Kōsaka clan of Makinoshima in the Sarashina District of Shinano Province.  The Kōsaka were the only clan aligned with the Takeda located in the border area between the Takeda territory on one side and, on the other side, the territory of Uesugi Kenshin and kokujin, or provincial landowners, based in northern Shinano who were opposed to the Takeda.  It is surmised that Toratsuna inherited the Kōsaka clan in view of the political and military position of the clan in the area of Kawanakajima.

According to the military chronicle known as the Kōyō gunkan, Toratsuna was adopted by the Kōsaka clan in 1561 when the clan was subject to punishment for colluding with Uesugi Kenshin.  In 1556, after Oyamada Masayuki (Bitchū-no-kami) was transferred from Kaizu Castle in the Minochi District to Amakazari Castle, Toratsuna served as his successor, becoming the chamberlain of Kaizu Castle.  At this time, he used the surname of Kōsaka.  Kaizu Castle, however, was built in 1560, so there is a discrepancy.  Meanwhile, according to the family register of the Takeda family at the Seikei Temple on Mount Kōya, as of 1558, he called himself Kōsaka Danjō.  His use of the Kōsaka surname appears in records from the eleventh month of 1559 until the sixth month of 1563 or, at the latest, again in the ninth month of 1566.  Based on authenticated sources, his real name was Toratsuna while Masanobu (which can also be read as Shōshin) is regarded as a name adopted to enter the priesthood.

Further, the name of Danjō is regarded as a nickname and frequently appears as Kōsaka Danjō.  Until 1559, he called himself Danjōzaemon-no-jō and, thereafter, changed to Danjō-no-jō.


In 1527, Toratsuna was born as the son of Kasuga Ōsumi, a peasant in the Isawa township in the Yatsushiro District of Kai Province.  In 1542, after the death of his father, Ōsumi, he lost to his older sister and her husband in an adjudication of the estate and was left without relatives but then engaged as an attendant to Shingen.

Initially, Toratsuna served as a messenger and, in 1552, became the general of a battalion of 100 ashigaru, or light infantry soldiers.  At this time, he adopted the name of Kasuga Danjō-no-jō.  A written pledge from Takeda Harunobu dating from 1546 and kept at Historiographical Institute, the University of Tokyo indicates that he had an amorous relationship with Toratsuna who is referred to under the name of Kasuga Gensuke.  The practice of pederasty was not uncommon during this period.

In 1553, after the Takeda clan commenced attacks against Murakami Yoshikiyo, a sengoku daimyō in the Hanishina District of northern Shinano, Toratsuna became the chamberlain of Komoro Castle in the Saku District.  In the fourth month of the same year, Toratsuna inherited the vestiges of the Kōsaka clan, kokujin in Maki-no-shima in the Sarashina District of Shinano, to serve the Takeda family.

Later, Toratsuna led a group from Kawanakajima including the Kōsaku clan and was assigned to the defense of the Kaizu territory on the front lines against the Uesugi clan of neighboring Echigo Province.  Toratsuna served as an intermediary with the Terao and Yashiro clans of northern Shinano as members of the Kawanakajima group.  Kaizu Castle was located on the front lines of the struggle between the Takeda and Uesugi clans.  In the eighth month of 1561, after an invasion by Uesugi Kenshin, Toratsuna holed-up in Kaizu Castle and, on 9/4 of Eiroku 4 (1561), leading to the Fourth Battle of Kawanakajima.

During an attack on Mount Saijo, Toratsuna contributed as a member of a detached battalion.  Thereafter, he continued to engage in the governance of northern Shinano and serve in the major battles of the Takeda clan including, in 1572, at the Battle of Mikatagahara.

Service to Takeda Katsuyori

After the death of Shingen in the fourth month of 1573, Toratsuna served Takeda Katsuyori and was delegated the role of chamberlain of Kaizu Castle as a stalwart against the Uesugi clan.  On 5/21 of Tenshō 3 (1575), during the Battle of Nagashino, Toratsuna did not participate and instead defended Kaizu Castle.  His lineal heir, Kōsaka Masazumi, was killed in action during the battle.  Under Katsuyori, clan members including Takeda Nobutoyo and Anayama Nobutada, in addition to hereditary retainers such as Atobe Katsusuke and Nagasaka Mitsukata, gained prominence while Toratsuna and other veterans were alienated.

At the Battle of Nagashino, the Takeda suffered a major defeat to the Oda.  The loss of many capable retainers in the Takeda family caused instability in their territory and the battle proved to be a decisive factor in the ensuing decline of the clan.  In the wake of the defeat, Katsuyori fled to Shinano and, on 6/2, returned to Kōfu.  Upon receiving news of the defeat, Toratsuna came to meet Katsuyori at Komaba in Shinano.  There is a story that Toratsuna provided Katsuyori with a change of clothing and armaments to avoid the appearance of a defeated army and preserve their honor.  He further provided a set of five proposals.  Whether Toratsuna did in fact provide these proposals is not certain but are deemed to have included strengthening the alliance with the Gohōjō clan of Sagami Province, promoting the children and younger brothers of Naitō Masatoyo, Yamagata Masakage, and Baba Nobuharu to serve as attendants and to reorganize the band of retainers, and, to have relatives including Anayama Nobutada and Takeda Nobutoyo who absconded from the battlefield take responsibility for the defeat by committing seppuku.

In the era of Katsuyori, the Takeda were in conflict with the Oda clan.  Meanwhile, in 1578, the death of Uesugi Kenshin led to a succession struggle in the Uesugi family known as the Otate Conflict.  At this time, Toratsuna, together with Takeda Nobutoyo, served as an intermediary with Uesugi Kagekatsu and was involved in the forging an alliance between the Takeda and the Uesugi known as the Alliance between Kai and Echigo.  Toratsuna’s name last appears in historical records in a letter dated 6/8 of Tenshō 6 (1578) from Kagekatsu addressed to Hōjō Takahiro and Hōjō Kagehiro during negotiations for the alliance.  In a letter from Nobutoyo dated on 6/12, Nobutoyo is participating on his own in the negotiations while, from the tenth month, Toratsuna’s son, Kōsaka Masamoto, appears in records.  Toratsuna is deemed to have died on 6/14 at Kaizu Castle.  He was fifty-two years old.

The date of Toratsuna’s death is the subject of various theories.  According to one account, the date was 5/11 of Tenshō 6 (1578), and according to another, 5/7 of the same year as indicated on his grave at the Myōtoku Temple.  This is inconsistent with the timing of negotiations conducted between the Takeda and Uesugi clans.  Based on the death register of the Takeda family kept at the Seikei Temple on Mount Kōya, his death occurred at 10:00 AM on 6/14 of Tenshō 6 (1578), which appears to be the most consistent with other records.  In another account of the Takeda family, his nephew, Sōjirō, held a memorial service at the Seikei Temple on 7/25 while Toratsuna’s posthumous Buddhist name was given on 4/21 of Kōji 2 (1556).

Descendants and the Kōyō gunkan

The Kasuga clan was inherited by Toratsuna’s second son, Nobutatsu, who became the chamberlain of Kaizu Castle.  The Takeda were extinguished by the Oda clan in the third month of 1582, Nobutatsu came under the command of Mori Nagayoshi.  On 6/2 of Tenshō 10 (1582) Nobunaga died in a coup d’état known as the Honnō Temple Incident.  Nobutatsu hindered Nagayoshi during his retreat to Mino Province by affiliating with Uesugi Kagekatsu of Echigo.  On 7/13, Nobutatsu was exposed for colluding with former retainers of the Takeda, namely, Sanada Masayuki and Hōjō Ujinao, who sought establish an independent base of power in northern Shinano.  This upset Kagekatsu who then murdered Nobutatsu, thereby ending the direct lineage of the Kōsaka clan.  In the third month of 1600, the remaining members of Nobutatsu’s family were tracked down in Shinano by Mori Tadamasa (Nagayoshi’s younger brother) and were summarily crucified as punishment for the crimes committed by Nobutatsu when he hindered Nagayoshi’s retreat from Shinano eighteen years earlier.

In early modern times, Yamamoto Kinemon, an elder from the town of Kōfu (also known as Kasuga Masayasu who lived from 1751 to 1836), originated from the Katō family who operated a large store, wakamatsuya, below Kōfu Castle.  The Katō family called themselves descendants of Toratsuna.

The Kōyō gunkan is a military chronicle completed in the Genna era of the Edo period detailing the exploits of Toratsuna while serving as a retainer of Takeda Shingen and Takeda Katsuyori.  According to its postscript, the original version was recorded on the basis of oral dictations from Toratsuna.  After the Battle of Nagashino, Toratsuna became concerned about the future of the Takeda clan and admonished in writing Katsuyori and his senior retainers including Atobe Katsusuke and Nagasaka Torafusa.

After the death of Toratsuna, his nephew, Sōjirō, and a retainer named Ōkura Hikojūrō, continued authoring the chronicle which was then completed by Obata Kagenori, the son of Obata Masamori, a subordinate of Toratsuna when Toratsuna served as the chamberlain of Kaizu Castle.

According to Kōsaka Setsuzō, an ancestor of the Kōsaka family named Kōsaka Danjō-no-tada Masanobu served Takeda Shingen.  His older brother, Kōsaka Masataka, was very proud of being the descendant of a bushō from the Sengoku period and named his eldest son Masanobu.


There is a story that Toratsuna was more than twice as strong as Shingen at the board game of igo.