Following the Seinan War in 1877, he joined the group planning raising a samurai army in Tohoku region, however, before the action, he was arrested and imprisoned as well as the other followers (the incident has been called 'Sanada Taiko Jiken' after the name of the ringleader who was a Shinto priest).
明治10年（1877年）の西南戦争に呼応して、東北地方での士族挙兵の計画に参画するが未然に検挙され（首謀者の神職の名から「真田太古事件」と呼ばれる）、他の参加者らとともに禁固刑に処せられた。