This Nobuyasu's incident has many unclear points including Tokuhime, who is believed to be the source of accusation, begging Ieyasu for a permission to go to see Nobunaga in the Azuchi Castle for the sake of Nobuyasu's defense (Ieyasu TOKUGAWA theory by Sohachi YAMAOKA), and in recent years there is a theory which suggests the discord between Ieyasu and Nobuyasu to be the cause.
事件の発端となったはずの徳姫自身が信康弁明の為に安土に居る信長に会いに行くと家康に頼み込んだりするなど（山岡荘八著徳川家康(山岡荘八)による説）、信康切腹事件に関しては不可解な点が多く、近年では家康と信康の対立が原因との説も出されている。