Some local historians believe that the Yasui clan lost many families at the time of the attack of Hongan-ji Temple, and that only Sadatsugu survived, which is why he had no encumbrances.
郷土史家のなかには、安井氏は本願寺の攻撃を受けた際に多くの一族を失い、定次一人が生き残ったものと思われることから係累がない。