The Nagaoka Residence is one of the Important Traditional Buildings located within the Ochiai Important Preservation District for Groups of Traditional Buildings in Higashi-Iya, Miyoshi City.
Situated on a south-facing slope at an elevation of about 610 meters, the house stands on the lower middle part of the Ochiai district. Locally known as "Wakidoi" or "Nishidoi", the Nagaoka family belonged to the ruling class of the Ochiai community.

The house follows the “kuchigai-rokumadori” (staggered six-room) layout, a distinctive floor plan found in Iya Valley. Unlike typical Iya-style farmhouses, it does not have a formal "omote" room at the front. Instead, it features a guest room with a "tokonoma" (alcove) and "shoin" (study area).
The "doma" (earthen floor area) is unusually small, and the toilet, usually located along the main facade, is positioned on the gable side. These features make the Nagaoka Residence quite unique compared to other traditional houses in the Iya region.

The pillars are about 13.5 cm square, with "toga" (Japanese hemlock) used around the guest room and "kuri" (chestnut wood) used elsewhere. Structurally, the house is characterized by thick beams and open spaces where vertical supports are omitted, particularly across the lower beam span, where three large beams extend without any supporting pillars.

According to a ridge tag (munafuda) found inside the building, the house was constructed in 1901 (Meiji 34).
Between 2007 and 2009, Miyoshi City carried out a full restoration with support from the national and prefectural governments to preserve and enhance the district’s historical landscape. The restoration was completed in March 2010, and today the Nagaoka Residence is open to the public as a facility introducing the history and charm of the Ochiai Preservation District.