Yataro is born into a poor family in Tosa Province (modern-day Kochi Prefecture).

After returning to Tosa following a family emergency, Yataro angers a local magistrate and is imprisoned. After his release, Yataro enters a school established by Toyo Yoshida (an influential Tosa official).

Yataro is dispatched to Nagasaki by the Tosa Clan, but then loses his position after returning home without permission to seek a loan. Yataro buys back his family's samurai status. At 27, he marries Kise and their first son, Hisaya, is born.

Yataro takes up a post at the Tosa Clan's Nagasaki trading office, where he meets Ryoma Sakamoto^*.
*A heroic figure from Japanese history during the days leading up to the Meiji Restoration.

Yataro is placed in charge of the Tosa Clan's Osaka trading office and then supervises Tsukumo Shokai after it is established by Tosa samurai.

Yataro assumes the management of Tsukumo Shokai after the government abolishes clan rule. The company takes the name of Mitsukawa Shokai and then later becomes Mitsubishi Shokai.

The company changes its name to Mitsubishi Jokisen Kaisha (Mitsubishi Steamship Company).

The company establishes regular service between Yokohama and Shanghai. It adopts the name Yubin Kisen Mitsubishi (Mitsubishi Mail Steamship) and becomes a favored enterprise of the Japanese government. Mitsubishi Iron Works is established.

Mitsubishi wins the trust of the government through its handling of military transport during the Satsuma Rebellion and builds a strong financial base.

Mitsubishi supports the establishment of Tokio Marine Insurance Company and continues to diversify its business, entering such fields as copper mining, finance and warehousing, water services, and insurance.

Mitsubishi purchases the Takashima Coal Mine and supports the establishment of Meiji Life Insurance.

Fearing the failure of both companies, the government negotiates a merger of the two companies and Nippon Yusen is established the following year. Yataro leases the Nagasaki shipyard from the government.

At Yataro's bequest, Yanosuke takes over the company. Mitsubishi is later passed on to Hisaya and Koyata, and Yataro's legacy continues to live on today through "the Mitsubishi companies".