According to the "Kasuga no Tsubone Ryakufu" (literally, The Abridged History of Kasuga no Tsubone), which was completed in 1686 after the death of Iemitsu, Tsubone remonstrated with Takachiyo (Iemitsu)--who had tried to commit suicide out of anguish that his parents, Hidetada and his wife, were overly fond of Takechiyo's biological younger brother, Kunimatsu (whose adult name was Tadanaga TOKUGAWA), and in 1615 she appealed directly to the 'Ogosho' (leading or influential figure) Ieyasu TOKUGAWA, who was living in retirement in Sunpu (what is today the city of Shizuoka), asking him to confirm that the Shogunal succession would pass to Takechiyo.
家光死後の貞享3年（1686年）に成立した『春日局略譜』によれば、秀忠夫妻が竹千代の実弟・国松（徳川忠長）を溺愛している様子を憂慮し、自害しようとした家光を諌め、元和元年、駿府にいた大御所の徳川家康に竹千代の世継を確定させるように直訴したとされる。