Izumi Family Residence Dressing Room and Drying Area

A Workshop for Drying Bonito, Rebuilt After the Earth Shook

On the southwest corner of the Izumi family's second floor, a slim room pushes out over a gateway. The ground level below is a passage that people walked through; the floor above it was where the household got skipjack tuna ready for the slow work of becoming katsuobushi. A short distance away, an open-sided shed faces the inner courtyard. This is the drying yard, where racks of fish caught the sun and the salt breeze coming off the harbor.

The two structures are registered together as a single property: the Izumi Family Residence Preparation Room and Drying Yard, in the fishing town of Usa in Tosa City, Kochi Prefecture. They are small, a combined footprint of only about 21 square meters, but they belong to a working household that turned fresh bonito into one of the most prized dried-fish products in Japan.

What the Buildings Are

The preparation room sits against the upper floor of the main house, on its southwest side. It measures roughly 2.7 by 1.8 meters, runs on a north-south axis, and carries a gabled roof. Its outer walls are finished in horizontal clapboard, and its lower story serves as a service gate into the property. Workers used the room above as a staging space for handling the fish before the next stage.

The drying yard is a single-story shed, about 5.5 by 2.7 meters, also aligned north to south and roofed with pantiles under a gable. Its courtyard side is left fully open, with no wall. That openness was the point: split and partly dried bonito needs air and sunlight, and an open frame let workers move racks in and out and let the breeze pass straight through.

Both date to around 1947. They were built as part of a wider rebuilding after the Showa Nankai Earthquake of December 1946, which struck this stretch of the Pacific coast hard. The main house that anchors the property was reconstructed at the same time, a wooden two-story building of about 92 square meters whose upper floor opens into a twenty-mat hall. A separate katsuobushi production house stands on the south side of the lot, near the harbor, with four interior rooms for the distinct stages of the craft: boiling, smoking, mold-culturing, and storage.

Why It Is Registered

The property is a Registered Tangible Cultural Property, not a designated one. The distinction matters. Japan's better-known tiers, National Treasure and Important Cultural Property, involve strict controls and are reserved for objects and buildings judged to be of the highest national value. The registration system, introduced in 1996, was designed for a broader and more everyday range of structures, especially those from the modern period that shape the character of a place. It applies a lighter regulatory framework, mainly asking owners to notify authorities before major alterations, which makes it well suited to buildings that are still lived in or used.

The Izumi buildings were registered on 29 November 2004 under the criterion of contributing to the historic landscape of the country. They are not celebrated for rare craftsmanship or great age. Their value lies in being a near-complete set: a private home, a production house, a preparation room, and a drying yard, all from the same postwar moment, all tied to a single trade. Read together, they show how a family in Usa organized the space of katsuobushi making, from the boiling kettle to the rack in the sun.

What to Notice

Stand back from the main house and look at the gable wall. It carries five tiers of mizukiri-gawara, narrow ledges of tile set into the plaster to throw rainwater clear of the wall. This is a regional habit of southern Shikoku, where typhoons drive rain sideways, and it gives Tosa houses a layered, ribbed profile you rarely see elsewhere.

The drying yard rewards a slower look. An open-sided structure is unusual to register and protect, because there is so little of it: a frame, a roof, and the empty space beneath. But that emptiness is the working logic of the building. Picture it filled with wooden racks, the courtyard smelling of smoke and sea, and the function becomes plain.

The production house, though a separate registration, completes the picture. Its four rooms follow the sequence of the craft. Bonito is boiled, then smoke-dried over a wood fire in repeated sessions, then deliberately cultured with a beneficial mold and dried again, a cycle repeated until the fish hardens into a piece said to be among the hardest foods in the world. A finished honkarebushi, the fully cultured grade, can take roughly half a year to make.

Around Usa

Usa calls itself the birthplace of improved Tosa-bushi. Local tradition holds that more than three centuries ago a fisherman from Kishu, in present-day Wakayama, came ashore here and shared techniques for smoke-drying and lowering the moisture of the fish. Craftsmen in Usa refined the method further with smoking and mold-culturing, and the resulting Tosa-bushi earned a high reputation. In a national ranking of dried bonito from 1822, products from Usa and nearby ports placed near the top.

The town that grew from this trade is small, home to a few thousand people, and laced with narrow lanes that still carry the scent of smoking fish on the right day. At its peak Usa had around forty katsuobushi houses; only a handful remain. To walk it well, the Tosa City Tourism Association runs a guided food-tasting stroll through the harbor district, including a stop at a working katsuobushi maker, with samples along the way. Booking ahead is sensible, since what you can see at a working factory depends on the day's tasks.

The harbor itself is worth time. Its hooked, whale-shaped cape served as a visual model for the fishing-town setting in a well-known Japanese animated film, and boats run whale-watching trips offshore in the warmer months. A Saturday market gathers at the fishing cooperative.