Sanayama Family Residence: A Window into Edo-Period Post Town Life on the Nakasendo

Standing quietly along the old Nakasendo highway in the town of Mochizuki, the Sanayama Family Residence (真山家住宅, Sanayama-ke Jūtaku) is one of the most authentic surviving examples of an Edo-period inn and merchant house in Nagano Prefecture. Designated as a nationally Important Cultural Property since 1973, this remarkable building—together with its traditional storehouse (dozō)—offers visitors a rare glimpse into the daily life and commerce that once thrived along Japan's historic inland highway connecting Edo (Tokyo) and Kyoto.

Known by its trade name "Yamatoya" (大和屋), the Sanayama family operated this building as both a tonya (wholesale shipping agent) and hatago (traveler's inn) during the Edo period, and by the end of the era, the family had risen to serve as nanushi—the village headman of Mochizuki-juku. The residence that stands today was rebuilt in 1766 (Meiwa 3), just one year after a devastating fire swept through the post town in 1765, and it has survived for over 250 years as a testament to the craftsmanship and resilience of its builders.

The Nakasendo and Mochizuki-juku: Historical Context

The Nakasendo (中山道, literally "Central Mountain Route") was one of the five major highways established by the Tokugawa shogunate during the Edo period (1603–1868). Stretching approximately 534 kilometers from Nihonbashi in Edo to Sanjo Ohashi in Kyoto, the Nakasendo offered an inland alternative to the coastal Tokaido road. Along its route, 69 post towns (shukuba) provided lodging, meals, and logistical support for travelers, including feudal lords (daimyo) making their obligatory journeys to and from the capital.

Mochizuki-juku (望月宿) was the 25th of these 69 stations, situated in what is now Saku City in eastern Nagano Prefecture. The town takes its name from the Mochizuki clan, a powerful local family that controlled the area from the Heian through the Sengoku periods. Their hilltop castle, Mochizuki Castle, once overlooked the town, and the remains of this fortification can still be visited today. Under the Tokugawa system, Mochizuki-juku developed into a bustling waypoint where travelers could rest, resupply, and exchange horses for the next leg of their journey.

Architecture of the Main House (Shūoku)

The main house of the Sanayama Residence is a masterpiece of mid-Edo townhouse architecture. Its overall dimensions are impressive: the main structure measures 10.9 meters in width (ketayuki) and 17.8 meters in depth (harama), with a partially two-story layout under a kirizuma-zukuri (gabled) roof covered with san-kawarabuki (pantiles). An extension on the north side adds another 9.8 meters by 4.6 meters of fully two-story space.

One of the most distinctive features of the building is its degeta-zukuri construction—a style in which the second floor projects slightly outward beyond the first, supported by extended beams (degeta). The bracket arms (udegi) that support these projecting beams are decorated with fine carvings, while the second-floor lattice windows (kōshi-do) rest on cloud-shaped ornamental brackets (mochisokuri), adding an air of elegance to the facade.

The front exterior walls are finished in white plaster (shikkui) over a true-wall (shinkabe) frame. The side elevation features horizontal weatherboarding (shitamibari), and the area beneath the eaves is coated with fire-resistant plaster—a practical measure against the spread of fire in the densely built post town. The deliberately low eaves reflect Edo-period regulations that restricted the height of merchant-class buildings, giving the structure its characteristically restrained profile.

Inside, the residence features elements of shoin-zukuri, the formal architectural style associated with samurai residences and reception halls. This combination of commercial townhouse layout with refined interior appointments speaks to the Sanayama family's elevated status within the community. The first floor retains shitomi-do (hinged lattice shutters) and wooden sliding doors at the entrance—typical fittings of an Edo-period inn—while the second floor is enclosed by the elegant kōshi-do lattice screens that are such a defining feature of the building's appearance from the street.

The Storehouse (Dozō)

Behind the main house stands the family's traditional storehouse (土蔵, dozō), a compact but solidly built two-story structure measuring 4.5 meters in width and 3.6 meters in depth. Like the main house, it has a kirizuma-zukuri gabled roof with pantile roofing. The storehouse is included in the Important Cultural Property designation alongside the main house, recognized as an integral part of the residential compound.

Dozō storehouses were essential features of prosperous merchant and innkeeper households throughout the Edo period. Their thick earthen walls, often reinforced with layers of plaster, served as protection against fire, theft, and moisture—safeguarding valuable goods, documents, and household treasures. The Sanayama family's dozō, standing in its original position at the rear of the property, completes the picture of a well-appointed post town merchant residence and helps visitors understand the full scope of daily life and commerce in Mochizuki-juku.

Why Was It Designated an Important Cultural Property?

The Sanayama Family Residence was designated a nationally Important Cultural Property (重要文化財) on June 2, 1973. Several factors contributed to this recognition.

First, the building has a clearly documented construction date of 1766, making it one of the few mid-Edo-period townhouses in the region whose age can be verified with certainty. This precise dating gives the residence exceptional value as a benchmark for understanding architectural development during this era.

Second, the residence preserves the architectural features of a post town inn and shipping agency with remarkable integrity. Although minor alterations were made during the Tenpo era (around 1841) and some second-floor modifications occurred during the Meiji period, the essential structure and character of the building remain true to its 18th-century origins.

Third, the building provides an invaluable comparison with other surviving hatago buildings along the Nakasendo. The official designation notes that, compared to the nearby Ono Family Residence (a fellow inn in Shiojiri), the Sanayama house shows a less developed second story and a more archaic structural approach. Together, the two buildings illustrate the evolution of post town inn architecture over the course of the Edo period.

The combination of the main house and storehouse as a unified ensemble further enhances the property's cultural significance, as it represents the complete layout of a prosperous post town household.

Highlights and What to Look For

When visiting the Sanayama Family Residence, be sure to observe the following features from the street:

• The projecting second-floor lattice windows (degeta-zukuri), supported by carved cloud-shaped brackets—a hallmark of prosperous Edo-period inns.
• The white plaster exterior walls, contrasting with the horizontal weatherboarding on the side—demonstrating traditional fire-prevention techniques in a densely built post town.
• The low eaves, a characteristic of Edo merchant architecture reflecting building height restrictions of the time.
• The old "Yamatoya" (大和屋) signage, evoking the building's long history as one of Mochizuki-juku's most prominent inns.
• The traditional storehouse (dozō) at the rear, with its thick plaster walls designed to protect against fire and the elements.

Because the building is a private residence, interior visits require advance reservation. Even without entering, however, the street-facing facade offers a powerful impression of Edo-period post town aesthetics and is a rewarding subject for photography.

Exploring the Surroundings

The Sanayama Family Residence sits within the broader historic landscape of Mochizuki-juku, and a leisurely walk through the area reveals many other points of interest.

The Mochizuki Historical and Folklore Museum (望月歴史民俗資料館) occupies the site of the former honjin (official inn for feudal lords) and offers exhibitions on three themes: local history and culture, life along the Nakasendo at Mochizuki-juku, and the traditions and daily life of the townspeople. This is an excellent starting point for understanding the broader context of the post town.

Nearby, the former wakihonjin (secondary official inn) of the Takano family still displays its Edo-period lattice facade and elegant carpenter's detailing. Other historic buildings along the old highway include the former residences of the Yasukawa and Odai families, both of which served as tonya during the Edo period.

A short walk brings you to Otomo Shrine (大伴神社), the guardian shrine of the Mochizuki area, and Joko-in Temple (城光院), the family temple of the Mochizuki clan. For those with time and energy, the ruins of Mochizuki Castle on the hillside above the town offer panoramic views of the Saku plateau and the surrounding mountains.

The neighboring Motai-ainoshuku (茂田井間の宿), located between Mochizuki-juku and Ashida-juku, is also worth a visit. This beautifully preserved "intermediate rest station" features well-maintained old warehouses and sake breweries that line the quiet streets, offering a remarkably atmospheric walk. The Saku area is renowned as a sake-brewing region, with thirteen breweries producing fine local sake—many of them open for tours and tastings.

Visiting Tips

The Sanayama Family Residence is located in a quiet, rural area that rewards unhurried exploration. Visitors arriving by public transportation can take a bus from JR Sakudaira Station (on the Hokuriku Shinkansen line) toward Mochizuki, with the ride taking approximately 20 to 25 minutes. By car, the residence is about 20 minutes from the Saku Interchange on the Joshinetsu Expressway. Alternatively, Shinano Railway's Komoro Station connects to Mochizuki by bus in roughly 25 minutes.

Because the building is privately owned, interior viewing is available only by prior arrangement. Even from the outside, however, the facade and the surrounding streetscape provide a vivid picture of Edo-period post town life. The adjacent Mochizuki Historical and Folklore Museum is open to the public and provides valuable background information for appreciating the area.

Spring and autumn are particularly pleasant times to visit, when mild weather and seasonal colors enhance the historic atmosphere. The town's annual Sakaki Festival (榊祭り) is a vibrant local event that brings the old streets to life with torches and a spirited portable shrine procession.