However, when the Sakuradamongai Incident occurred in tandem with his retirement life, on July 2, 1860 Tadahiko was suddenly captured by Fushimi Magistrate's office on suspicion of involvement in the incident.
だが、隠居と相前後して桜田門外の変が起こると、忠彦は同年（万延元年に改元）5月14日(旧暦)、事件への関与の疑いで突如伏見奉行に捕らえられる。