This was Japan's first anime (animated feature).
Begun in 1942, not completed and released until 1945.
The film was considered lost for decades, as the American occupation authorities confiscated and destroyed most known copies of it. A negative copy of the film was discovered in an old warehouse in 1983. It became the source for the home video versions of the film, from 1984 on-wards.
The film was commissioned by the Ministry of the Navy (1872-1945), which was abolished during the post-war Allied occupation of Japan (1945-1952).
The director of the film, Mitsuyo Seo, was reportedly instructed to imitate American animation methods in this film. Seo reportedly used "Fantasia" (1940) as his main source of inspiration.