Kaganoi Shigemochi served as a bushō and daimyō during the Sengoku and Azuchi-Momoyama periods. He was the lord of Kaganoi Castle in Mino Province.
In 1561, Shigemochi was born as the son of Kaganoi Shigemune. His childhood name was Yahachirō. Initially, he served Oda Nobunaga and, after his death, he served Nobunaga’s second son, Oda Nobukatsu.
Nobukatsu awarded Shigemochi the township of Kaganoi as a fief, and Shigemochi became the lord of Kaganoi Castle.
In 1584, at the Battle of Komaki-Nagakute, Shigemichi commanded a garrison of 2,000 soldiers including Ozaka Oyoshi. On 5/4, a large army commanded by Hashiba Hideyoshi surrounded the castle. On 5/5, Nobukatsu informed Fuwa Genroku Hirotsuna (the lord of Takegahana Castle) that Hideyoshi was laying siege to Kaganoi Castle, and on 5/7, sent a letter to Tokugawa Ieyasu requesting to send Genroku as a rear guard to Kaganaoi. However, on 5/5, Hideyoshi’s forces set fires to Takegahana and Sobue, and broke through the exterior walls of Kaganoi Castle, leaving only the moats for defense. On 5/7, just before the castle was toppled and garrison commanders beheaded, Shigemochi and his father escaped through a side gate. Kanbe Yogorō, the commander-in-chief of the reinforcements, also escaped, but his eldest son, Kanbe Jūzō and approximately 1,000 soldiers died.
Thereafter, the Kaganoi clan was invited by Hideyoshi to accept assignments; however, after the violent toppling of Kaganoi Castle, Shigemune found it against his conscience to serve Hideyoshi so he retired. Shigemochi served as a scout for Hideyoshi and was awarded a fief of 8,000 (or 10,000) koku in Kaganoi.
On 7/19 of 1600, approximately two months prior to the Battle of Sekigahara, during a banquet with Mizuno Tadashige and Horio Yoshiharu at a station on the Tōkai Road in Chiryū in Mikawa, Shigemochi slayed Tadashige during an argument over a trifling manner. Shigemochi also stabbed Yoshiharu multiple times with a spear but was finally killed by Yoshiharu. He was forty years old. In the wake of this incident, the Western Army seized the landholdings of the Kaganoi clan.
After the Western Army suffered an ignominious defeat, Shigemochi’s son holed-up in Ōgaki Castle. After the fall of the castle, he was executed by Tadashige’s son, Mizuno Katsunari.
Shigemochi was known for excelling in the military arts. He put up stiff resistance after Kaganoi Castle was surrounded by a large Toyotomi army. After the battle, Hideyoshi recognized his valor and promoted him to the rank of daimyō.
The Battle of Komaki-Nagakute may have been a reason for Shigemochi to have become upset with Tadashige. In that conflict, after Kaganoi Castle was surrounded by enemy forces, Shigemochi requested reinforcements but none were sent. While the defenders were routed, Shigemochi and his father narrowly escaped.
Rather than killing Tadashige and wounding Yoshiharu over a minor issue, Shigemochi may have been secretly ordered by Ishida Mitsunari (one of the leaders of the Western Army) to gain intelligence with respect to the movements of the Eastern Army (in advance of the Battle of Sekigahara) or to assassinate an important person (Tadashige was the uncle of Tokugawa Ieyasu while Yoshiharu was an influential bushō in the Eastern Army). This theory, however, is only recorded in the Tokugawa Chronicles and does not align with the seizure by the Western Army of the landholdings of the Kaganoi clan after the incident.