[1] After becoming disillusioned with Toei due to complaints about production staff being unable to propose projects, he quit in 1961 and joined Mushi Pro on hearing that Osamu Tezuka was going to make anime.
Sugii helped refine Tezuka's rough animation into proper keys on the Tetsuwan Atom (Astro Boy) pilot film.
[3] In 1964, Sugii along with Atsushi Takagi, Osamu Dezaki, Seiji Okuda and others left Mushi Pro and established studio Art Fresh.
[3] In 1967, Sugii made his directorial debut with Mushi Pro’s television series Adventures of the Monkey King (Goku no Daibôken).
[4] After promoting Manga Nippon Mukashibanashi [ja], Sugii decided to spend some time away from the anime industry, setting off to travel the country from the mid-1970s to the early 1980s before finally returning to helm Night on the Galactic Railroad.