was a retainer beneath the clan of Oda

Oda clan

The was a family of Japanese daimyo who were to become an important political force in the unification of Japan in the mid-16th century. Though they had the climax of their fame under Oda Nobunaga and fell from the spotlight soon after, several branches of the family would continue on as daimyo...

 throughout the latter Sengoku Period

Sengoku period

The or Warring States period in Japanese history was a time of social upheaval, political intrigue, and nearly constant military conflict that lasted roughly from the middle of the 15th century to the beginning of the 17th century. The name "Sengoku" was adopted by Japanese historians in reference...

 of Feudal Japan. Shigetsuna was the legitimate second son of Gamō Sadahide and was later adopted by Aochi Nagatsuna, a daimyo

Daimyo

is a generic term referring to the powerful territorial lords in pre-modern Japan who ruled most of the country from their vast, hereditary land holdings...

 who held residence in the Kurita District of Omi province

Omi Province

is an old province of Japan, which today comprises Shiga Prefecture. It was one of the provinces that made up the Tōsandō circuit. It is nicknamed as .Lake Biwa, Japan's largest lake, is located at the center of the province...

. Around the year of 1569 Shigetsuna along with his brother Gamo Katahide would both submit to the prominent Oda Nobunaga

Oda Nobunaga

was the initiator of the unification of Japan under the shogunate in the late 16th century, which ruled Japan until the Meiji Restoration in 1868. He was also a major daimyo during the Sengoku period of Japanese history. His opus was continued, completed and finalized by his successors Toyotomi...

. One year following this event Shigetsuna accompanied his new lord in a campaign that would aspire for death to the defiant Asakura

Asakura clan

The ' are descendants of Prince Kusakabe , son of Emperor Temmu .The family was a line of daimyō which, along with the Azai clan, opposed Oda Nobunaga in the late 16th century...

 of Echizen province

Echizen Province

was an old province of Japan, which is today the northern part of Fukui Prefecture. It was sometimes called , with Etchū and Echigo Provinces.Echizen is famous for washi . A text dated AD 774 mentions the washi made in this area. Echizen-produced Washi is still the most commonly sold traditional...

. However, after Asai Nagamasa had initially defected from his allegiance to the Oda in support of the Asakura, who were his mutual allies for many generations, the Oda army was forced into retreat and Shigetsuna would consequently lose his life defending their rear guard.