 In November 1920, he was awarded with the Grand Cordon of the Order of the Golden Kite and the Grand Cordon of the Order of the Rising Sun.Ōi was ennobled with the "kazoku" peerage title of "danshaku" (baron) in April 1921, and entered the reserves in March 1923.From March 1924, he served as a member of the House of Peers in the Diet of Japan.