In the early fifth century large keyhole-shaped mounds appeared; these Kofun were similar in size to the Obo class (tomb of the King or Emperor) mounds, located upon the Kawachi Plain from within the regions of the Nara Basin.
5世紀の初頭、王墓クラスの大型前方後円墳が奈良盆地から河内平野に移った。