02/09/2026
Yayoi Settlements on the Shiwaku islands.
The red dots on the Shiwaku map mark a scatter of small Yayoi-period (roughly 300 BCE–300 CE) sites. These islands sit in the fast currents of the Bisan-Seto, so the settlements were maritime hamlets, not the rice-paddy villages typical of river plains on Honshu or Shikoku.
Hiroshima: the best-known site is Shinkyōzan (心経山), a high-ground settlement on a ridge with a wide view of the shipping lanes. Similar lookout villages appear on nearby mainland headlands such as Shiudeyama.
Honjima and Mukaijima: a Yayoi site is recorded on Mukaijima; coastal and low-ridge spots on Honjima itself also produced pottery and tools.
Yoshima / Hitsuishijima / Iwakurojima area: smaller coastal and hill-slope scatters. Shamijima’s Nakanda Beach site is better known for Jōmon layers, but salt-working features continue into Yayoi and Kofun.
The settlements were modest—usually a handful of pit-houses (round or later rectangular, sunken floors, thatched roofs) plus a few raised-floor storehouses. No large moated “towns” like Yoshinogari have been found here. People chose ridges and coves that combined a bit of cultivable slope, fresh water, and a clear sight-line over the strait.
Wet-rice farming existed on the islands only in tiny patches; the main living came from the sea: fishing, shellfish, and especially salt. Salt-making pottery and simple evaporation hearths appear from the Middle Yayoi onward—the same industry that later gave the archipelago its name (塩焼く / “salt boiling”). The islands also sat on the east–west sea road that carried bronze, iron, and pottery between Kibi, Sanuki, and the Kinai region, so the hamlets doubled as way-stations and lookout posts.
From the Middle Yayoi, many Seto Inland Sea communities moved onto hills with good views. Archaeologists read this as a mix of defense, signaling, and control of shipping during a period of growing inter-group tension. The Shiwaku sites fit that pattern: small groups watching the same channels that later produced the famous Shiwaku mariners.
