[1] The Naruto Itano Kofun cluster is located along an eleven kilometer area at the southeastern foot of the Asan Mountains, which crosses the northern part of Tokushima Prefecture from east to west.

The Amanokawawake Jinja Kofun cluster (天河別神社古墳群) was threatened with destruction due to prefectural road construction in 1978 and the Ōshiro Kofun cluster (大代古墳群) was likewise treated by construction of an extension of the Cross-Shikoku Expressway in 2000.

A burial chamber made of crystalline schist class contained a box-shaped wooden coffin aligned east-to-west.

Although resembling a keyhole-shaped tomb, it predates true zenpō-kōen-fun by a couple of centuries, leading to much speculation by archaeologists on its design.

The Amanokawawake Jinja Kofun Cluster (天河別神社古墳群) consists of at least 11 tumuli, of which only No.1 through No.4 are protected by the National Historic Site designation.

2 is also an enpun [ja]-style circular mound with a diameter of about 26 meters, built close on the same ridge as Amanokawawake Jinja Kofun No.1.

The Hōdōji Kofun (宝幢寺古墳) is a keyhole-shaped tumulus built on a north-south ridge at an elevation of 27 to 32.5 meters.

However, during the Edo Period, the posterior circular portion of the tumulus was highly modified to hold the tombs of the chief priests of the Buddhist temple of Hōdō-ji, which destroyed the burial chamber.

The Ōshiro Kofun (大代古墳) is a keyhole-shaped tumulus built on a north-south ridge at an elevation of 41 to 47 meter.

The Ōshiro Kofun is part of a cluster containing two smaller enpun-style round tumuli.