[1][2] Tadakatsu was born in Nishio, Mikawa Province as the son of Sakai Tadatoshi, a hereditary retainer of Tokugawa Ieyasu and future daimyō of Kawagoe Domain.

Also in 1643, he was involved in the "Nanbu Incident", when ten sailors (including the captain) of the Dutch Ship Breskens were taken into custody by local Japanese officials.

[6] The Dutch ship had visited the bay once before seeking to resupply after a heavy storm, and quickly left after trading with the locals for two days.

[7] However, when the Breskens returned in July the ship and its crew were seized by local authorities for its violation of Japan's national isolation policy.

[8] This sparked an international incident, and at the time the rōjū serving the shogunate were Sakai Tadakatsu, Matsudaira Nobutsuna, and Inoue Masashige.

[11] This book was brought from Japan to Europe by Isaac Titsingh in 1796, who translated the text from Japanese and Chinese; and his work was then supplemented for posthumous publication by Julius Klaproth in 1834.