However, especially during the period of the mid-third century to the late sixth century, these were the years of the 'Kofun period' in which the Japanese people built many keyhole-shaped mounds throughout the northern territory of the 'Tohoku Region' and the southern 'Kyushu region'; therefore, this period would sometimes be referred to as the 'keyhole-shaped mounds period.'
が、中でも3世紀半ば過ぎから6世紀末までは、前方後円墳が北は東北地方から南は九州地方の南部まで造り続けられた時代であり、前方後円墳の世紀ともいわれる。