Sadao is a unisex given name of Japanese origin, meaning 'just right' or 'in harmony'. It is composed of two kanji characters: 'Sad' (定) which means 'fixed', 'firm', or 'established', and 'Ao' (青) that signifies 'blue'. In Japan, the name Sadao has been traditionally used for males, but it can also be found among females. The name gained international recognition through the character Sadao Nakamoto in Yukio Mishima's novel 'The Temple of the Golden Pavilion'.
The name Sadao experienced varied popularity from 1914 to 1934, with the highest number of births recorded in 1922 at 21. However, there was a significant decline after this peak, reaching as low as 7 births in both 1931 and 1934. The total number of births over this period was 244.