Iwao Family Residence (Former Nihongan Pharmaceutical Works)

About the Iwao Family Residence (Former Nihongan Pharmaceutical Works)

The Iwao Family Residence (Former Nihongan Pharmaceutical Works) (岩尾家住宅（旧日本丸製薬所）, Iwao-ke Jūtaku, Kyū Nihongan Seiyakusho) is the set of buildings of Iwao Yakuho, a pharmacy founded in 1855 in Mameda-machi, Hita City, Oita Prefecture, and its main house, storehouse and annex, built between the early Meiji era and the early Showa era, became Registered Tangible Cultural Properties on January 31, 2003. The word Nihongan in the name has nothing to do with a ship, despite the familiar maru of Japanese vessel names: it was a small pill the shop made, read nihon-gan, with gan meaning pill.

Today the buildings open to visitors as the Nihongan-kan (日本丸館), a small museum, while Iwao Yakuho still trades next door. With its third-floor lookout, the main house is known locally as the castle keep of Mameda, a nickname the Agency for Cultural Affairs records in its own description. Guidebooks may also call the place Iwao Yakuho Nihongan-kan or the Iwao Pharmacy; all refer to the same buildings.

Iwao Yakuho and the Nihongan Pill

According to the Nihongan-kan, Iwao Yakuho opened for business in 1855. In 1887 Iwao Shotaro, the fifteenth head of the family, began making and selling Nihongan, marketed as a cure-all. Sales took off, and the firm opened branches in Tokyo, Osaka, Kyoto, Nagoya and Sapporo, as well as in Korea and Manchuria. At its height the pill was sold as far away as Hawaii and Brazil.

Production of Nihongan stopped in 1965. The buildings opened as a museum in 1993, showing pill-making tools, old packaging, advertising and the family's household goods. The words "former pharmaceutical works" in the official name of the Iwao Family Residence look back to those manufacturing years.

The Nihongan-kan also describes the Iwao Family Residence as the first building designated under Hita City's urban landscape program.

The Iwao Family Residence in the Mameda Townscape

Mameda-machi grew up as the merchants' quarter of Hita when the town was a shogunate domain in the Edo period, and on December 10, 2004 it was selected as an Important Preservation District for Groups of Traditional Buildings. Hita City's summary explains that after great fires in 1772, 1880 and 1887, thatched townhouses were rebuilt in the Igura-zukuri manner, with tiled roofs and timber framing sealed under earthen plaster. Alongside these fireproofed townhouses of the Edo to Taisho eras, the district also keeps a few three-storey houses from the early Showa era.

The Agency for Cultural Affairs places the main house of the Iwao Family Residence at the center of Mameda Kami-machi, a street where the old townscape survives. A white-walled townhouse with one more storey perched on top, it is easy to pick out above the low rooflines.

The Three Buildings and Their Registration

The Agency for Cultural Affairs database describes the layout and dates of the three buildings of the Iwao Family Residence as follows.

• The main house faces the street. It was built in the late Taisho era as a 2-storey Machiya townhouse, and a third-floor lookout was added in the early Showa era. It is a 3-storey wooden building with a footprint of 171 square meters.
• The storehouse adjoins the north side of the main house and turns its gable end to the street. It is a 3-storey storehouse from the late Meiji era, with a footprint of 62 square meters.
• The annex stands behind the main house and is reached by a 2-storey connecting corridor. It dates from the early Meiji era and has a footprint of 60 square meters.

All three buildings were registered together on January 31, 2003, with the official notice following on February 26, under the consecutive numbers 44-0091 to 44-0093. The main house and the storehouse were registered for contributing to the historic landscape of the country, and the annex for being difficult to reproduce. The oldest of the three is the annex at the back, and the newest is the main house on the street.

The Nihongan-kan describes the building as wooden, with four levels and three floors. In visiting order, the reception and kitchen are on the first floor; the medicine room, the Nihongan exhibition room, the great hall, the roof garden and the retirement room are on the second; and the storehouse parlor and the lookout are on the third. Some tourist guides say the building grew by stages from a single-storey Edo-period house, but this page follows the dates given by the Agency for Cultural Affairs.

Visiting the Iwao Family Residence (Former Nihongan Pharmaceutical Works)

The interior of the Iwao Family Residence (Former Nihongan Pharmaceutical Works) opens as the Nihongan-kan in spring and autumn. The spring season runs February 15 to May 31 and the autumn season September 1 to November 30, with opening hours of 10:00 a.m. to 4:00 p.m. There are no closing days within these seasons, apart from a few days around mid-April when the displays are changed. Admission is 400 yen for adults and 200 yen for elementary, junior high and high school students, with 50 yen off per person for groups of 15 or more.

Outside the two seasons the museum opens irregularly, and between June and August and between December and February 14 visitors may not be able to enter because of maintenance work on the building and its equipment. If the entrance is shut, ask at Iwao Yakuho next door and the staff will show you in. Temporary closures for repairs are announced on the museum's official Instagram account, so check ahead if you are coming from far away. The building has no air conditioning, and summer afternoons can be hot inside. These details were checked against the official Nihongan-kan website and the Oita Prefecture tourism site on October 6, 2026.

The museum is about a 15-minute walk from Hita Station on the JR Kyudai Line. There is no dedicated parking. The second floor of Iwao Yakuho is a rental space called Gallery Ren, entered through the gateway on the left of the building.