Shotoku's conduct on this occasion has inspired much censure and surprise when contrasted with his conspicuous respect for virtue in all other cases. But the history of the time requires intelligent expansion. Cursory reading suggests that Umako's resolve to kill Sushun was taken suddenly in consequence of discovering the latter's angry mood. The truth seems to be that Sushun was doomed from the moment of his accession. His elder brother had perished at the hands of Umako's troops, and if he himself did not meet the same fate, absence of plausible pretext alone saved him. To suffer him to reign, harbouring, as he must have harboured, bitter resentment against his brother's slayer, would have been a weakness inconsistent with Umako's character. Sushun was placed on the throne as a concession to appearance, but, at the same time, he was surrounded with creatures of the o-omi, so that the latter had constant cognizance of the sovereign's every word and act.
When the o-omi judged the time fitting, he proposed to the Emperor that an expedition should be despatched to recover Mimana, which had been lost to Japan some time previously. An army of twenty thousand men, commanded by a majority of the omi and muraji, was sent to Tsukushi, and all potential opponents of the Soga chief having been thus removed, he proceeded to carry out his design against the Emperor's life. The very indignity done to Sushun's remains testifies the thoroughness of the Soga plot. It has been shown that in early days the erection of a tomb for an Imperial personage was a heavy task, involving much time and labour. Pending the completion of the work, the corpse was put into a coffin and guarded day and night, for which purpose a separate palace was* erected. When the sepulchre had been fully prepared, the remains were transferred thither with elaborate ceremonials,** and the tomb was thenceforth under the care of guardians (rioko).
*Called Araki-no-miya, or the "rough palace." The interval during which time the coffin remained there was termed kari-mo-gari, or "temporary mourning."
**Known as kakushi-matsuri, or the "rite of hiding." It would seem that the term of one year's mourning prescribed in the case of a parent had its origin in the above arrangement.