Deep-Sea's Rainbow

Deep-Sea's Rainbow, known in Japan as Ningyo Hime, was produced by Toei Animation and released in 1975. The film serves as a loose, ambitious adaptation of Hans Christian Andersen’s The Little Mermaid, created as part of the studio's mid-70s effort to expand their cinematic reach beyond television series. It arrived during a period of experimentation for Japanese animation, where filmmakers were increasingly blending traditional fairy tale narratives with the distinct, melancholic aesthetic that would later define the Studio Ghibli era.

The film was directed by Tomoharu Katsumata and features character designs by the legendary Yoichi Kotabe. Kotabe, who would later become a pivotal figure in the animation departments of both Nintendo and Toei, aimed for a stylized, ethereal look that departed from the rigid realism of Western animation. Upon its debut, the film was noted for its fluid movement and unique color palette, receiving critical appreciation for its poetic atmosphere, though it remains a deeper, more esoteric entry in the classic pantheon of mermaid-themed cinema.