The succession may be said to have had three aspirants at that time: first, Prince Karu, younger brother of the Empress Kogyoku; secondly, Prince Naka, her son, and thirdly, Prince Furubito, uncle of Soga no Iruka. The last was, of course, excluded from Kamatari's calculations, and as between the first two he judged it wiser that Prince Karu should have precedence in the succession, Prince Naka not being old enough. The conspiracy that ensued presents no specially remarkable feature. Kamatari and Prince Naka became acquainted through an incident at the game of football, when the prince, having accidently kicked off his shoe, Kamatari picked it up and restored it to him on bended knee. The two men, in order to find secret opportunities for maturing their plans, became fellow students of the doctrines of Chow and Confucius under the priest Shoan, who had been among the eight students that accompanied the Sui envoy on his return to China in the year 608.
Intimate relations were cemented with a section of the Soga through Kurayamada, whose daughter Prince Naka married, and trustworthy followers having been attached to the prince, the conspirators watched for an occasion. It was not easy to find one. The Soga mansion, on the eastern slope of Mount Unebi, was a species of fortress, surrounded by a moat and provided with an armoury having ample supply of bows and arrows. Emishi, the o-omi, always had a guard of fifty soldiers when he went abroad, and Iruka, his son, wore a sword "day and night." Nothing offered except to convert the palace itself into a place of execution. On the twelfth day of the sixth month, 645, the Empress held a Court in the great hall of audience to receive memorials and tribute from the three kingdoms of Korea. All present, except her Majesty and Iruka, were privy to the plot. Iruka having been beguiled into laying aside his sword, the reading of the memorials was commenced by Kurayamada, and Prince Naka ordered the twelve gates to be closed simultaneously. At that signal, two swordsmen should have advanced and fallen upon Iruka; but they showed themselves so timorous that Prince Naka himself had to lead them to the attack. Iruka, severely wounded, struggled to the throne and implored for succour and justice; but when her Majesty in terror asked what was meant, Prince Naka charged Iruka with attempting to usurp the sovereignty. The Empress, seeing that her own son led the assassins, withdrew at once, and the work of slaughtering Iruka was completed, his corpse being thrown into the court-yard, where it lay covered with straw matting.