In 1858, accused of his sealing a written pledge of the assassination scheme of Roju (senior councils of the Tokugawa shogunate) Akikatsu MANABE planned by Shoin with his blood, he was put under house arrest by his uncle in his mother's line, Tasuke SHIRANE.
安政5年（1858年）、松陰の老中間部詮勝暗殺計画に血盟をしたことから、外叔の白根多助により家に幽閉される。