Born in 1709 as the fourth son of the 6th shogun Tokugawa Ienobu. With his older brothers having died young, he became the 7th shogun in 1713 at the age of 4 (by Japanese counting)—the youngest shogun in the history of the Tokugawa shogunate. Due to his youth, real power was held by chamberlain Manabe Akifusa and Confucian scholar Arai Hakuseki in what was called 'inner-circle governance.' In 1716, his betrothal to Princess Yaso, daughter of Emperor Reigen, was arranged, but he died of acute pneumonia from a worsened cold on April 30 that same year at the age of 8 (6 by modern counting). His death ended Ienobu's bloodline, and the shogunate passed to Tokugawa Yoshimune of Kishu.

Few records of his personality survive due to his youth, but he is said to have been an intelligent and well-mannered child. He reportedly conducted himself with dignity even when receiving Korean envoys.

A tragic shogun who reigned only 3 years and died at 8. Yet his death brought Tokugawa Yoshimune of Kishu to power, triggering the Kyoho Reforms that revitalized the shogunate. He symbolizes a turning point in history.