The tombs do not appear in any historical records and the name of rank of the persons buried within are unknown, although per local legend, these were the graves of the "Kings of Koshi" (越の国), the pre-imperial dynasty state which controlled present-day Fukui, Ishikawa, Toyama and Niigata Prefectures.

Emperor Keitai ((reigned 507 – 531 AD)) is said in some semi-legendary historical records to have originally been the King of Koshi, and therefore that the kofun in this area are the tombs for members of his clan.

The details of the interior are unknown as the kofun has not been excavated; however, ground-penetrating radar has confirmed that a stone-lined burial chamber exists near the apex of the posterior circle.

Torigoeyama Kofun (鳥越山古墳) is the smallest of the four tumuli, with a total length of 53.7 meters; however, it was found to have a boat-shaped stone sarcophagus and two horizontal passage graves.

A large number of grave goods were also uncovered, including stone spearheads, whetstones, fragments of iron implements, earthenware and horse fittings.

It is built facing southwest on the summit of Nihonmatsuyama at an elevation of 273 meters on the south bank of the point where the Kuzuryu River enters the Fukui Plain.