His grandfather was a samurai and governor of Echigo Province Mitsui Takayasu, who was later exiled to Matsusaka after being defeated by Oda Nobunaga.
Mitsui's father Takatoshi abandoned his katana, thus renouncing his status as a samurai, and established himself as a sake and miso merchant and a pawnbroker.
He moved to Edo at 14 years of age, following his eldest brother Toshitsugu who had extended the family business by opening a kimono store (呉服屋, gofukuya)[2] there in 1627.
He then established the Echigoya Drapery[4][3] in Nihonbashi the following year, which was to become, later, the head company of the famous Mitsukoshi retail shopping chain.
He extended the family business by opening an outlet in Osaka, and was appointed official purveyor of dry goods to the Tokugawa shogunate in 1687.