Nishiyama Palace Ruins (Nishiyamaso)

Seizansō: Where Tokugawa Mitsukuni Retired to Write Japan's Great History

The year before he gave up his domain, Tokugawa Mitsukuni — the second lord of Mito and one of the most powerful men in seventeenth-century Japan — picked out a narrow valley in the far north of the Kantō plain and decided he would die there. When the residence was finished, he gave the bridge at the village entrance a name borrowed from a fourth-century Chinese fable: Tōgenkyō, the Peach Source Bridge. In Tao Yuanming's tale, a fisherman drifts up a stream lined with peach blossoms and into a hidden world cut off from the dynasties and wars beyond. Mitsukuni was telling anyone who could read the reference exactly what he intended this place to be.

What survives today, on roughly 14.3 hectares at the head of the Genji River, is the villa he called Seizan-gyoten — the West Mountain Residence — known now simply as Seizansō, the West Mountain Lodge. It is a one-storey thatched building with mud walls, set behind a gate that opens onto a small valley of ponds, cedars, and maples. For a man who had inherited a 350,000-koku stockpile and ruled one of the three branches of the Tokugawa house, the modesty is the point.

The man who began the Dai Nihonshi

Tokugawa Mitsukuni (1628–1700) was born the third son of Tokugawa Yorifusa, founding lord of Mito. He took over the domain in 1661 at the age of thirty-three and threw the resources of his administration behind a project he had begun privately a few years earlier, in 1657: a chronological history of Japan, written in classical Chinese in the manner of the great Chinese standard histories. The work, eventually titled Dai Nihonshi ("Great History of Japan"), would consume two and a half centuries of Mito scholarship before its completion in 1906. It sent researchers across the country to copy archives, dispatched a samurai-scholar named Sasa Munekiyo on a famous tour of cultural sites, and quietly seeded the school of historical thought that would help bring down the shogunate his own family had founded.

In 1690 Mitsukuni was sixty-two and tired. He passed the domain to his adopted son Tsunaeda, retreated to Seizan, and adopted the name Seizan Inshi — the West Mountain Recluse. He moved in the following year and stayed until he died here in the winter of 1700.

Retirement, for him, was not retirement. From this small house he kept editing the manuscript of the Dai Nihonshi, sponsored the repair of the Nasu Kuni-no-miyatsuko stele in Tochigi (now a National Treasure), and ordered the excavation of the nearby Samuraizuka burial mound — one of the earliest examples of antiquarian archaeology in Japan. He toured his own villages. He released deer into the surrounding hills and red-crowned cranes into the rice fields below the house, and planted Chinese quince, plum, and kumazasa bamboo grass — all of them medicinal — across the grounds.

Why both a Historic Site and a Place of Scenic Beauty

In March 2016 the Agency for Cultural Affairs designated Seizansō as both a National Historic Site (shiseki) and a National Place of Scenic Beauty (meishō). It was only the second property in Ibaraki Prefecture to receive both honours at once. The two categories cover different things. The Historic Site designation recognises the residence as the place where Mitsukuni edited the Dai Nihonshi by hand — a monumental site in the history of Japanese scholarship. The Place of Scenic Beauty designation covers the gardens, ponds, and surrounding cedar groves, which the Mito Tokugawa house preserved with unusual care for more than three centuries.

The current residence is not the original. Mitsukuni's house was dismantled after his death, rebuilt in 1716 to mark the seventeenth anniversary of his passing, then destroyed by a brush fire in 1817. The structure visitors enter today went up two years later, in 1819, under the eighth Mito lord Narinobu. It is a faithful reconstruction at one-third the original scale, raised from the same surveys and floor plans that had been preserved in the family's records. Despite the reduction, the layout of gates, ponds, paths, and waterfall has held to the Genroku-period original — which is the part of Mitsukuni's vision the cultural agency considered worth protecting.

Walking the grounds

The approach is on foot, from a parking area through a free public garden called Nishiyama-no-Sato. Visitors pay at a ticket gate and continue uphill past the Kumano cedars — a stand of conifers said to have been a gift from the Kii Tokugawa family, planted at Mitsukuni's instruction and now overhead. A small stone-paved path leads to the Tsukiage-gomon, the formal front gate, with its distinctive swing-up shutter.

The villa itself is small. Six tatami rooms in a row — entrance hall, audience room, retainers' anteroom, sleeping room, study — and a row of sliding doors that open onto the south garden. The study, the ogakumon-jo, is three mats with a single round window. The detail visitors are usually told to notice is the missing threshold between Mitsukuni's room and the room his attendants used: a deliberate omission, by tradition explained as his wish that conversations across rank should not be physically partitioned. Whether or not that reading is historically airtight, the absence of the sill is real, and unusual.

Look up at the ridge of the thatched roof and you will see ichihatsu — roof iris — planted along its crest. This is not decorative. The plant's roots help bind the thatch and shed water, and a passage in the early eighteenth-century chronicle Tōgen Iji records that iris was already growing on the ridge in Mitsukuni's own time.

The south garden centres on two ponds joined by a low channel. The upper one, Hakuren-ike or White Lotus Pond, is also called Shinji-ike because its outline traces the character for "heart" (心). Water once ran from it eastward over a small carved-stone waterfall called Otaki — fed, as a 1968 repair confirmed, by a hand-cut rock tunnel from a neighbouring valley — and down into Kōren-ike, the Red Lotus Pond, shaped like a gourd. Above the waterfall rises Kangetsu-zan, "Moon-Viewing Mountain", where Mitsukuni is recorded to have held viewing parties on autumn nights. The waterfall is dry today, but the stone framing of the falls remains.

Around Hitachiōta

Seizansō sits in a quiet pocket of forested hills at the northern edge of the Kantō plain, where the Genji River begins. The neighbourhood is rural — small rice paddies, a few houses — and once you are inside the gate the modern world drops out. Plan an hour and a half to two hours at the site itself, longer in autumn when the maples colour.

Two other Mitsukuni-related sites are very close. Zuiryūsan, the Mito Tokugawa family cemetery, contains the grave of his father Yorifusa and is also a designated Historic Site. Kyūshō-ji, his mother's family temple, is a short drive away. Further afield, Hitachiōta has hot-spring bathhouses in the Yamabuki area, and Fukuroda Falls — one of Japan's three great waterfalls — is about forty minutes by car. The Ryūjin Suspension Bridge, 375 metres long over a reservoir, is in the same direction.

Spring brings plum blossom along the entrance path; June, irises beside the ponds; November, the maples Mitsukuni recorded planting on the ridges. Winter, when the thatch is sometimes dusted with snow, is the season visitors who have read the Tōgen Iji tend to come for.