That is unreliable as a historical fact because it was a record of folklore told by people over a hundred years after the duel, however, the description is quite similar to the description in "Numatake-ki" which was re-discovered recently and regarded as reliable material.
あくまでも試合から100年以上経った時代の民間伝承の記録であり、史料としての信頼性は低いが、近年再発見された『沼田家記』の記述に類似している。