Hirao gained experience working at the animation studio MADHOUSE. After leaving MADHOUSE, he entered ufotable and was in charge for animation direction. His debut work was ”Kara no Kyoukai: Paradox Spiral” in 2008. After that, he directed works like ”Magical Sisters Yoyo and Nene” and ”GOD EATER”. He then left ufotable and eventually became a freelancer. He is now working on his new movie.