Because the Kira family, the head of the clan, had been brought to an end since the Genroku Ako Incident, Yoshitoshi had been requesting permission from the bakufu to change their surname Maita back to Kira.
元禄赤穂事件以来、本家の吉良家が断絶していたため、義俊は、姓を蒔田から吉良に戻す許可を幕府に求めていた。