There are many unanswered questions to this incident, with theories other than Imai assassinating Ryoma, including a theory holding that the assassination was by feudal retainers or warriors of Satsuma and another interpretation by Jiro ASADA in his "Mibu Gishin Den"
この事件に関しては不可解なことが多く、上の今井信郎説のほかにも、薩摩藩士説や、浅田次郎の『壬生義士伝』のような解釈も行われている。