Upon graduating from Nihon University's art department's school of film, Miyaji took part in Studio Ghibli's Higashi-Koganei Sonjoku training program in 1998.[1][2] He studied under the program along with fellow future animator Tadashi Okumura.[1][2] The promise he showed in the program led him to be selected as assistant director to Hayao MiyazakiinSpirited Away.[1]
In 2008, he made his full directorial debut with Xam'd: Lost Memories.[1] In an interview to The Japan Times, Miyaji stated that he believed anime was a part of the film industry and said, in respect to Xam'd's "theatrical dimension", he had wished to use an "almost documentary style" for certain parts and listed directors Ken Loach and Jean-Luc Godard as his inspirations.[3] He also stated with the series' unique PlayStation Network release, he felt he could reach out to a "different kind" of audience.[3]
