The Oyamato tumulus group and Yanagimoto tumulus group, which include the Makimuku remains related to the birth of the Yamato regime, in the southeast part of the Nara basin, as well as mausoleums of emperors in the Yamato regime, in the area from the southern part of Tenri City to Sakurai City, declines, and huge keyhole-shaped tumuli in this group became to be constructed in the era from the latter half of the fourth century to the first half of the fifth century.
奈良盆地の東南部のヤマト政権誕生に関わりのある纏向遺跡や天理市南部から桜井市にかけて初期ヤマト政権の大王墓を含む大和古墳群・柳本古墳群が5世紀初頭には衰退し、本古墳群が4世紀後半から5世紀前半に巨大前方後円墳を営むようになった。