Ogasawara Nagatoki served as a bushō and as a sengoku daimyō of Shinano Province.  Nagatoki was the head of the Shinano-Ogasawara clan.  He served as the lord of Hayashi Castle.

In 1514, Nagatoki was born as the eldest son of Ogasawara Nagamune.  He was from the family of the Ogasawara school of archery, horsemanship, and etiquette.  Nagatoki is counted among the Four Great Generals of Shinano.

On 11/5 of Daiei 6 (1526), Nagatoki attended his coming-of-age ceremony at the age of thirteen.  He is surmised to have inherited the headship of the clan in 1541 when his father, Nagamune, entered the priesthood.  From around this time, he served as the head of the family.  Nagamune died in 1542.

In the neighboring province of Kai, the Takeda clan serving as military governors unified the province.  The Kai-Takeda were members of the same Kai-Genji lineage as the Ogasawara clan.  After inheriting the headship of the Takeda clan in the same year that Nagatoki took command of the Ogasawara, Takeda Harunobu (Shingen) launched the Invasion of Shinano.  In 1545, Harunobu deployed to the Ina District for the purpose of eliminating Takatō Yoritsugu and Fujisawa Yorichika.  On 4/17, the Takeda forces toppled Takatō Castle defended by Yoritsugu.  Next, the Takeda attacked Yorichika (Nagatoki’s son-in-law) at Fukuyo Castle, whereupon, to the north, Nagatoki resisted against the Takeda forces from Ryūgasaki Castle.  After the Takeda received reinforcements from the Imagawa and the Hōjō, on 6/1, Itagaki Nobukata, a retainer of the Takeda, toppled Ryūgasaki Castle and Nagatoki withdrew in defeat.  Nagatoki was an intrepid warrior skilled in archery and horsemanship but struggled in the command of subordinates.

After taking control of the Ina District, the Takeda forces advanced to Saku and confronted Murakami Yoshikiyo, a powerful member of the kunishū, or provincial landowners, in the Chiisagata District.  In the second month of 1548, at the Battle of Uedahara in Chiisagata, Yoshikiyo trounced the Takeda.  In the fourth month,  Nagatoki, along with Yoshikiyo, Nishina Moriyoshi, and Fujisawa Yorichika invaded the Suwa District.  In the sixth month, with the support of groups from western Suwa, they further invaded Suwa and, on 6/19, pressed their offensive toward the Shiojiri Ridge but were repelled by the Takeda.  This is known as the Battle of Shiojiri Ridge.

On 7/15 of Tenbun 19 (1550), after Nagatoki lost his base at Hayashi Castle, the Shinano-Ogasawara clan fell into ruin.  That same year, Nagatoki presented to Ashikaga Yoshiteru, the thirteenth shōgun of the Muromachi bakufu), a long sword and horse via Ogasawara Tanemori of the Kyōto-Ogasawara clan (relatives of the Shinano-Ogasawara who served for generations as members of the hōkōshū, a military organ under the direct jurisdiction of the Muromachi bakufu).  Nagatoki promised to convey orders from the bakufu to members of the kunishū in Shinano.  After the fall of the clan, Nagatoki either relied upon the Futatsugi clan at Nakatō Castle to flee to Echigo Province or else he escaped to  Suzuoka Castle held by his younger brother, Ogasawara Nobusada.  His whereabouts thereafter are unknown.

According to one account, in 1555, he traveled through Suruga and Ise provinces, and, with the assistance of a relative, Miyoshi Nagayoshi, the lord of Akutagawayama Castle in Settsu Province, Nagatoki went to Kyōto and stayed in the environs of the capital.  The exact year is uncertain, but in a letter from this period written by Nagatoki to the Daigo Temple, he noted that Nagayoshi had recovered from illness after treatment from a physician named Manase Dōsan.  In reference to his own situation, he further said that he was providing instruction in the equestrian arts to Hosokawa Rokurō (later known as Hosokawa Akimoto) who was a hostage of Nagayoshi.

In Shinano, Murakami Yoshikiyo and other gōzoku, or wealthy families, from northern Shinano turned to Nagao Kagetora (Uesugi Kenshin) of Echigo while the Battle of Kawanakajima unfolded between the Takeda and Uesugi clans.  In 1558, as an aspect of the settlement between the Takeda and Uesugi, Takeda Harunobu (Shingen) was appointed the military governor of Shinano, but even after entering into the settlement, Harunobu continued military operations in the province.  Ashikaga Yoshiteru, the shōgun, then permitted Kagetora to intervene in Shinano.  In 1559, through mediation by Nagayoshi and Ise Sadataka, Nagatoki met Yoshiteru and received a cup of saké.  Yoshiteru, via Ōdachi Harumitsu, ordered Kenshin to assist in the return of Nagatoki to Shinano.

Beginning in 1562, to preserve the traditions of the Ogasawara school of archery and horsemanship originated by his ancestors, Nagatoki transferred the teachings, the genealogy, and records to a relative named Akazawa Tsunenao (Ogasawara Sadatsune), Hoshino Mian, and Koike Jin-no-jō Sadanari, entrusting the traditions of horsemanship and rules of etiquette of the main branch of the family to them.  This constituted an orthodox succession to the methods of instruction in archery, horsemanship, and etiquette.

In 1566, Nagatoki presented Ashikaga Yoshihide, the fourteenth shōgun, with a long sword and horse.  Yoshihide was backed by Miyoshi Yoshitsugu and Matsunaga Hisahide but, in 1568, the Miyoshi were expelled from the capital by Nobunaga and Ashikaga Yoshiaki was installed as the fifteenth and final shōgun of the Muromachi bakufu.  In 1569, during the Battle of Honkoku Temple, Nagatoki lost his younger brother, Ogasawara Nobusada.

After a while, Nagatoki went to the Uesugi clan in Echigo Province.  In 1578, the death of Kenshin triggered a succession struggle known as the Otate Conflict.  During this event, Nagatoki served as a messenger for Uesugi Kagetora, but after Uesugi Kagekatsu prevailed and succeeded to the headship of the clan, Nagatoki departed from Echigo.  In 1581, he was welcomed by Oda Nobunaga and served as a nominal leader in Shinano.  During the Kyōto Mounted Horse Parade led by Nobunaga, Nagatoki participated as a member of a group of nobles.  Later, he was received as a guest commander by Ashina Moriuji of Aizu in Mutsu Province.  Moriuji treated him well and Nagatoki managed support for Moriuji in the capacity of a military strategist.

On 2/25 of Tenshō 11 (1583), Nagatoki died in Aizu.  He was seventy years old.  His third son, Ogasawara Sadayoshi, did not accompany Nagatoki to the Ashina family and instead remained behind to serve Nobunaga.  There are traces of Sadayoshi serving Nobunaga from around the time of the Battle of Nagashino.  On 6/2 of Tenshō 10 (1582) Nobunaga died in a coup d’état known as the Honnō Temple Incident.  Thereafter, Sadayoshi submitted to Tokugawa Ieyasu and recovered the former territory of his father.

Cause of death

Nagatoki died in the second month of 1583.  There is a theory that he died of natural causes, but, under another theory, he was murdered (along with his consort and three daughters) by a retainer with the surname of Sakanishi.

According to historical accounts that attribute his cause of death to a slaying by the sword, Nagatoki was hosting a banquet at the residence of Tomita Ujizane, one of the Four Divine Kings of the Ashina.  At this time, Nagatoki engaged in sexual advances toward the wife of Sakanishi Shōsaburō.  Upset at the incident, Shōsaburō drew his sword and killed Nagatoki along with his wife and daughters.  Thereafter, Shōsaburō attempted to flee but was killed by Hoshi Aki-no-kami and Hinodeyama Akitsugu. 

With respect to the actions of Shōsaburō, it is noted that, owing to drunkenness, he may have overinflated or misinterpreted the situation, thereby killing Nagatoki’s family.

Informational materials from the city of Aizu-Wakamatsu to introduce local figures indicate that Nagatoki was killed by a retainer which is the same theory as is stated in the comprehensive dictionary of Japanese history.