The Eastern Expedition of Emperor Jimmu (Jimmu Tosei)

Kamuyamato Iwarehiko—the future Emperor Jimmu—was the grandson of Hoori and the great-grandson of the heavenly grandson Ninigi. Born and raised in Hyuga in southern Kyushu, he determined that this remote region was not suitable for ruling the entire land. With his elder brother Itsuse no Mikoto, he resolved to lead an expedition eastward to establish a capital in the center of the realm.

Setting out with their forces by sea, they traveled along the Inland Sea coast, stopping at various points to gather allies and provisions. In Naniwa (present-day Osaka), they attempted to advance inland but were met by fierce resistance from the local chieftain Nagasunehiko. In the battle, Itsuse was struck by an arrow and mortally wounded. As he lay dying, he realized their mistake: 'We fought facing the sun, which is why we were defeated. We must circle around and attack with the sun at our backs.'

The expedition detoured south, rounding the Kii Peninsula. Along the treacherous mountain paths, they faced natural barriers and hostile forces. At one critical juncture, the heavenly gods sent Yatagarasu—the great three-legged crow—to guide them through the impenetrable mountain wilderness. The divine bird flew ahead, and the army followed its path through the forests and valleys of Kumano.

In another desperate moment, when Jimmu's forces were felled by a mysterious supernatural poison that rendered them unconscious, a local man named Takakuraji brought a sacred sword (Futsu no Mitama) that had descended from heaven. When this blade was drawn near the sleeping warriors, they instantly revived, and the hostile spirits were vanquished.

After years of campaign, Jimmu finally confronted and defeated Nagasunehiko's forces. The chieftain's lord, Nigihayahi—himself of heavenly descent—recognized Jimmu's divine authority and surrendered. With the land pacified, Jimmu established his palace at Kashihara at the foot of Mount Unebi in Yamato Province. There, on the first day of the first month—traditionally dated to 660 BCE—he ascended the throne as the first emperor of Japan.

The eastern expedition thus completed the journey that began with the Tenson Korin: the heavenly authority, which had descended to Hyuga, was now established in Yamato—the heart of the Japanese realm.