Inaridai No. 1 Kofun, Ancient burial mound in Ichihara, Japan

Inaridai No. 1 Kofun is a round burial mound about 28 metres across in the Inaridai group on the north bank of the lower Yoro River in Ichihara. It was built after mounds No. 2 and No. 3 and holds two burial facilities, a central wooden coffin and a northern wooden coffin, in which two warriors were buried one after the other.

The Inaridai group of twelve mounds was excavated in 1976 and 1977. Mound No. 1, a 28-metre round tomb, was built after Mounds No. 2 and No. 3. Its two wooden coffins held warriors buried in succession: the central coffin dates to the mid-5th century, the northern one to its later part. The silver-inlaid sword was a gift from a king, likely a Yamato ruler.

The name Inaridai comes from the Inari shrine that once stood on this plateau above the Yōrō River. The two warriors buried here, one in the central coffin and one in the north coffin, are thought to have served a king and received the silver-inlaid sword as a reward. The burial goods show a direct link between the Yamato court and eastern warriors.

The mound can be viewed from the outside and information signs explain the archaeological findings on site. Visit during daylight hours when the display boards are most useful and the grounds are easy to navigate.

The sword's silver-inlaid inscription reads "王賜" (granted by the king), and the identity of that king is debated: some link him to the Yamato court, possibly Emperor Ingyō, while others argue he was the chieftain buried across the Yōrō River at the 103-metre Ōnatsuka burial mound. A similar inscribed sword came from Inariyama Kofun in Saitama.