Naito Masatoyo

Naito Masatoyo (1522-1575) was one of the "Takeda Four Heavenly Kings" who served Takeda Shingen and Katsuyori, a great general who led elite Takeda forces alongside Yamakago Masakage, Baba Nobuharu, and Kosaka Masanobu. He accumulated many military achievements in the conquest of Kozuke Province (present-day Gunma Prefecture), becoming lord of Minowa Castle and a key figure in Takeda control over the Kanto region.

Rising to prominence under Shingen's tutelage, Masatoyo excelled in battlefield command as a practitioner of Koshu-ryu military strategy. Participating in major Takeda campaigns including the Battles of Kawanakajima, his tactical brilliance was highly regarded by fellow generals.

The Battle of Nagashino (1575) became Masatoyo's final engagement. The Takeda army suffered a devastating defeat against the combined Oda-Tokugawa forces' musket formations at Shitaragahara, but Masatoyo stood firm until the end, heroically dying in battle while serving as the rearguard for the retreating Takeda forces. Praised as "Naito Shuuri is a great treasure of Takeda," his death was an irreplaceable loss for the Takeda clan.

In his connection to swords, Masatoyo is said to have had deep ties with swordsmiths of Koshu (Yamanashi) and Shinshu (Nagano), possessing fine swords as a general of the Takeda forces. His swords embodied the beauty of practical Japanese swords, befitting a warrior who had mastered Koshu-ryu military strategy.