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Ijuin Tada'aki(伊集院忠朗; 1520–1561) a retainer of the Japanese clan of Shimazu following the Sengoku period of the 16th century of Japan. Under Tada'aki, Ijuin clan would rise to the prominence as one of the most important retainer in the Shimazu clan.
He served under Shimazu Tadayoshi and Shimazu Takahisa was essential in uniting Shimazu clan, and battles against Ito clan and Kimotsuki clan. At the siege of Iwatsurugi in 1554, it was recorded that Tada'aki had his troop use matchlock guns against enemies for the first time by the Shimazu army. For this and other contributions and services, he held the post of the top karō until 1556 and governed as the top official of the clan.