Kimmei, the twenty-ninth emperor of Japan according to the traditional order of succession, and the first to whom contemporary historiography assigns clear dates, was the son of Emperor Keitai and Princess Tashiraka, Emperor Ninken's daughter.

Known during his lifetime by the name Amehara Oshiharaki Hironiwa or Amekuni Oshiharaki Hironiwa, he has established or moved his court to Shikishima no Kanazashi Palace in Yamato.

Mononobe no Okoshi and Nakatomi no Kanamura are both appointed Ōmuraji, and Soga no Iname is appointed Ōomi.

Although the imperial court will not move to the Asuka region of Japan until 592, Emperor Kimmei's rule is considered by some to be the beginning of the Asuka period of Yamato Japan, particularly those who associate the Asuka period primarily with the introduction of Buddhism to Japan from Korea.

With the introduction of a new religion to the court, a deep rift has developed between the Mononobe clan, who supported the worship of Japan's traditional deities, and the Soga clan, who supported the adoption of Buddhism.

Because of several temporal discrepancies in the account of Emperor Kimmei in the Nihon Shoki (sometimes translated as The Chronicles of Japan, an early eighth-century work written in classical Chinese, as is common for official documents at this time), some believe that his is actually a rival court to that of successive Emperors Ankan and Senka.

Bidatsu, the second son of Emperor Kimmei by his consort Iwahime, a daughter of Emperor Senka, had been appointed crown prince by his father; after Kimmei dies in 572, Bidatsu ascends to the throne within a few days.

Bidatsu rules during a tense period between the Soga and Mononobe clans regarding acceptance of Buddhism in Japan.

During his reign, he will have two empresses.

The first empress, Hirohime, had died in 577, the fifth year of his reign.

To replace her, he had elevated one of his consorts, Princess Nukatabe, to the rank of empress.

Nukatabe, his half-sister by their father Kimmei, will later ascend to the throne in her own right and is today known as Empress Suiko.

In external affairs, Bidatsu seeks to reestablish Japanese influence in Korea but is largely unsuccessful; according to Nihonshoki, his court establishes relations with Baekje and Silla.

Nagao Torachiyo was the third son of the head of Echigo province in northeastern Japan.

With the death of his father in 1543, the family's control of the area had begun to disintegrate.

Torachiyo had not only restored order to the area but also gained control of neighboring provinces, becoming one of the most powerful warriors on the Kanto Plain in central Honshu.

Uesugi Norimasa, who had inherited the position of kanrei, or governor-general, of Kanto and whose family had long been the most powerful in the area, had been defeated in 1552 by the Hojo clan and had taken shelter with Torachiyo, whom he had adopted as his son.

Torachiyo had then changed his surname to Uesugi.

He had received many of the hereditary vassals of the Uesugi family, and he had also become involved in a series of battles with the eastern warlords of the Hojo and Takeda families for control of the Kanto region.

Uesugi's battles with the noted general Takeda Shingen had resulted in no permanent gain for either side, however.

Meanwhile, Oda Nobunaga had become the strongest military leader in Japan, and in 1573 he had overthrown the shogunate and begun to consolidate his control over the capital.

The only warrior strong enough to challenge Oda is Uesugi, and in 1577 he agrees to undertake an expedition to restore the shogunate.

He dies, however, before the expedition can get under way.