Hidemasa was the eldest son of Hori Masashige. He was from Owari province and began his career in the service of Nobunaga. In 1581 he was ordered to conduct a land survey in Izumi and during the course of the survey the Makinoji (a branch temple of the Kongobuji of Mt. Koyo) took up arms on 11 June - Hidemasa attacked the temple and burned it. Later that year he was awarded Obama castle in Wakasa and in June 1582 joined in Toyotomi Hideyoshi's attack on Akechi Mitsuhide. He fought at Yamazaki and soon afterwards defeated Akechi Mitsuharu at Uchide-hama, near Otsu. He went on to secure Sakamoto castle, which became part of a large fief he was awarded in Omi worth 90,000 koku. Hidemasa participated in the Komaki Campaign (1584) on Hideyoshi's side, and led 3,000 men at the Battle of Nagakute. He joined the Toyotomi army besieging Odawara castle in 1590 but died in camp during the campaign.
- Initial text from Samurai-Archives.com FWSeal & CEWest, 2005