During the early days of the travel "the Narrow Road to the Deep North," he stayed in Senju for a long time, but there is no word in "the Narrow Road to the Deep North," so there is speculation that he was going to take on an assignment as a secret agent.
『奥の細道』の旅の初め千住に滞在した日数が多いのに『奥の細道』には消息がないため、隠密としての任務を受けに行っていたのではないかとの憶測がある。