While one theory places this event during the end of the Jōmon period, thus portraying the new arrivals as agrarian Yayoi tribes who came into conflict with indigenous Jōmon hunter-gatherers, others instead propose this conflict to have taken place during the late Kofun period (late 6th-early 7th century), when keyhole-shaped burial mounds containing equestrian gear as grave goods - up to this point found mainly in the Shimoina region southwest of Suwa - begin to appear in the Lake Suwa area, replacing the kind of burial that had been common in the region since the early 5th century. This theory thus supposes these migrants to have been a clan allied with the Yamato kingdom that specialized in horse breeding and horseback riding. Indeed, the Yamato polity showed strong interest to Shinano because of its suitability as a place for grazing and breeding horses and considered it a strategic base for conquering the eastern regions. This clan, the Miwa (Suwa), is thought to be related to either the Kanasashi clan (金刺氏), an offshoot of a local magnate clan (kuni no miyatsuko) that later became the high priestly family of the Lower Shrine of Suwa, or the Miwa (Ōmiwa) clan () originally based on the area around Mount Miwa in Yamato Province. The theory suggests based on archaeological evidence that the Miwa (Suwa) came to the Suwa Basin from Shimoina, making their way northwards along the Tenryū River. In conjunction with this hypothesis, it is pointed out that in the Nobushige Gejō (believed to be the earliest attestation of this myth), the Suwa deity is said to have descended from heaven bringing with him bells, a mirror, a saddle and a bridle.