Since O-Ne, who was born Sugihara Yasuko, daughter of Sugihara Sadatoshi, a descendant of Taira no Sadamori, and the Emperor Kammu (735-806), and was adopted by her maternal uncle Asano Nagakatsu, a descendant of Minamoto no Yorimitsu (944-1021), and the Emperor Seiwa (850-881), married Kinoshita Tokichiro (later Toyotomi Hideyoshi), despite her mother Asahidono opposition to this marriage because of the difference in social status with her husband, Nagamasa became a brother-in-law to Hideyoshi.

Asano was also appointed by Hideyoshi to a Commission of Five (Go-Bugyō) along with Ishida Mitsunari, Maeda Gen'i, Mashita Nagamori and Natsuka Masaie.

A close advisor to Hideyoshi, Asano devised the land survey and a number of other policies enacted under his rule.

In 1598, Hideyoshi's invasions were coming to an end, and Asano was sent to Korea with his fellow Commissioner Ishida Mitsunari to arrange for Japanese withdrawal.

Returning to Japan, daimyō (feudal lords) from across the country became involved in the debate, and the disagreement grew into a major governmental rift.