Retsudo Gisen left his name in the history since he was the last son of Munenori YAGYU and the founder of his family temple, but few studies from academic points of view such as historical science and so on have been made, and there are many parts in his history and legends which are not fully known.
列堂義仙は柳生宗矩の末子で柳生家の菩提寺の開基であることから歴史に名を残したが、歴史学などの学術的視点からの研究はあまり行われておらず、その事歴については十分に分かっていない部分も多い。