Hideharu was the eldest son of Hori Hidemasa. He was given Kasugayama in Echigo province after his father's death and in 1598 his domain was expanded to 350,000 koku around Takato. Just prior to the Sekigahara Campaign (August-October, 1600) Hideharu squabbled with Uesugi Kagekatsu of neighboring Aizu, although he was to play only a small role in the 'Eastern' campaign to defeat the Uesugi clan. He died at a young age, prompting some to question whether Tokugawa Ieyasu may have had a hand in his demise. His son, Hori Tadatoshi, was accused of incompetence in 1610, lost his fief at Takato in Echigo province, and was banished to Mutsu province.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005