Obata Toramori served as a bushō during the Sengoku period.  Toramori served two generations of the Takeda clan, Takeda Nobutora and Takeda Harunobu (Shingen), the sengoku daimyō family of Kai Province.  He was born as the son of Obata Nichijō (Moritsugu).

He was a retainer of the Takeda clan of Kai Province and named as one of the Five Famed Retainers of the Takeda – meritorious retainers who came from other provinces to serve under Nobutora and Harunobu.  The other members of the Five Famed Retainers of the Takeda included Hara Toratane, Yokota Takatoshi, Tada Sanpachirō, and Yamamoto Kansuke.

Toramori was also counted among the Twenty-Four Generals of the Takeda.  There is another Obata clan (written with a different character that has the same pronunciation) that was a military family from Kōzuke.  Toramori’s son, Obata Masamori, was permitted by Shingen to adopt the Obata surname with the character used by the family from Kōzuke.  Meanwhile, there are genealogies in which Toramori had a distant relationship to the Obata clan of Kōzuke.  His son-in-law was Ichikawa Tōchō.

Toramori originated from Tōtōmi Province, and he accompanied his father in service of Takeda Nobutora, moving to Kai Province in 1500.  In 1504, his father was killed during a deployment to subdue a rebellion by Imai Nobukore.  Toramori inherited the family at the age of fourteen.  Toramori served as a commander-in-chief of the ashigaru, or foot soldiers, under the command of Nobutora.  He engaged in battles to unify Kai Province as well as against clans from neighboring provinces including the Imagawa of Suruga and the Gohōjō of Sagami.  In 1521, when Fukushima Masanari, a retainer of the Imagawa, invaded Kai, Toramori joined Hara Toratane in the vanguard to intercept the attacking forces on the front lines.  Owing to his contributions in battle against the Imagawa and Hōjō clans, Toramori received one of the characters in his name from Nobutora, and adopted the name of Toramori.  Based on his military exploits, he was called the onitora, or Demon Tiger.

In 1541, after the expulsion of Nobutora, he served Shingen.  In 1551, after Shingen entered the priesthood, he joined Hara Toratane and Sanada Yukitaka by undergoing the rites of tonsure and adopted the name of Nichii.  During the Eiroku era (1558 to 1570), he entered Kaizu Castle (later known as Matsushiro Castle) as the lieutenant general to Kasuga Toratsuna and focused on opposing the Uesugi clan.  He died of illness in the sixth month of 1561 at the age of seventy-one.  In his will, he is known for saying “know your social standing.”  Toramori participated in thirty-six battles and received thirty-six commendations.  In the course of these battles, he incurred injuries in forty-one locations on his body, signifying the long record of this brave warrior.