Since then, Tadakuni had made remarkable progress under the shogun, Ienari, and got a promotion to Osaka jodai (the keeper of Osaka Castle) and was conferred the rank of Jushiinoge (Junior Forth Rank, Lower Grade) in 1825.
その後、将軍・家斉のもとで頭角を現し、文政8年（1825年）に大坂城代となり、従四位下に昇位する。