The culture introduced a centralized, patriarchal, and militaristic culture to the yayoi.

It is Kofun culture. It is a period of Japan's history from around 250 to 538 AD, following the Yayoi period. Kofun means "ancient burial mound" in Japanese. Burial mounds were built for the people of the ruling class during the 3rd to 7th centuries in Japan. 
During this period, the clans were leading powers. And in the head of each clan was some patriarch. It is also the period when militaristic rulers developed. Kofun period was known as the first centralization in Japan.