The Former Nishikawa Riemon House was the home of a prosperous family of merchants who made a fortune in the seventeenth century selling mainly mosquito nets and tatami mat surface covers. The first Nishikawa Riemon (1590–1646) established the family business by opening a store in Edo (now Tokyo) under the trade name Daimonjiya and another store in Osaka under the trade name Omiya. Thereafter, each successive head of the family took the name Nishikawa Riemon.

The third Nishikawa Riemon built the house on the west side of Shinmachi Street in 1706. The third Riemon’s younger brother Shoroku established his own branch of the family, whose members came to live across the street from the Riemon House and built a fine house of their own in 1785. In 1930, the eleventh Nishikawa Riemon passed away without a successor, and the main family came to an end. The Nishikawa Shoroku family endured, however, and had the Nishikawa Riemon House donated to the city of Omihachiman. In 1983, the building was designated an Important Cultural Property, and between 1985 and 1988, it was completely restored to its original appearance—that of a typical Omi merchant’s house of the Edo period (1603–1867).

The two-story house, now open to the public as a museum, was built with hemlock wood and has black-painted walls and a gabled, tiled roof. On the ground floor, the entrance porch, shop area, and kitchen have earthen floors, while the living areas have wooden floors. The floors in the reception rooms are covered with tatami mats. The shutters on the front of the house slide upwards, enabling this side of the building to be used as a shop. Various historical artifacts and artworks are on display inside the house. In the inner garden is a three-story fire-resistant storehouse with whitewashed walls, built between 1681 and 1683. Opposite the Nishikawa Riemon House stands the Nishikawa Shoroku House, which has been designated a Cultural Property of Shiga Prefecture.