The Rebellion of Tagishimimi (タギシミミの反逆)

The Rebellion of Tagishimimi is a tale of Japanese mythology that after Emperor Jinmu passed away, Tagishimimi devised a ploy to become the emperor but was defeated by Kamununakawamimi (later, Emperor Suizei) and his army.

Story Outline
In addition to three children he had with Himetataraisukeyorihime (Himetataraisuzuhime), Kamuyaimimi no Mikoto, Hikoyai no Mikoto, and Kamununakawamimi no Mikoto, the emperor (Emperor Jinmu) also had two children with Ahiratsuhime while he was in Himuka (Hyuga), Tagishimimi no Mikoto and Kisumimi no Mikoto. After the emperor passed away, Tagishimimi had a ploy to marry Himetataraisukeyorihime and kill her three children. Upon knowing his ploy, Isukeyorihime made a poem depicting clouds rising from the Sai-gawa River and leaves on the trees rustling on Mount Unebi to tell that it was a sign of a storm, to warn her three children. Her children understood the meaning of the poem and decided to kill Tagishimimi immediately.

Kamununakawamimi gave a weapon to his older brother Kamuyaimimi and told him to kill Tagishimimi. Kamuyaimimi failed, however, because his hands and legs were trembling, so Kamununakawamimi took the weapon from his older brother and gave the finishing blow to Tagishimimi. To praise his bravery, Kamununakawamimi is also called Takenunakawamimi. Ashamed of his failure, Kamuyaimimi gave up the Imperial throne to his younger brother Kamununakawamimi and served as a Shinto priest.

Explanation
The fact that among Emperor Jinmu's children, the youngest son Kamununakawamimi succeeded the Imperial throne indicates that there was a custom of postremogeniture in ancient Japan. Kamununakawamimi's father, Emperor Jinmu (Kamuyamatoiwarebiko), was also the youngest among four children of Ugayafukiaezu, whose father Hori was also the youngest child.

Although it was omitted in the story outline described above, Kamuyaimimi and Hikoyai, who didn't succeed the Imperial throne, were described as the founder of many clans. This description indicates that those clans intended to connect their ancestry to Emperor Jinmu to show their deep relationship with the Yamato Dynasty.