Chiisana Love Letter: Mariko to Nemunoki no Kodomo-tachi(1981)

A follow-up to the same studio's Helen Keller anime, A Little Love Letter kept the handicapped theme but focused on a wholly Japanese story. During the 1970s, actress Mariko Miyagi became heavily involved in the Silk Tree Academy (Nemunoki Gakuen), a rehabilitation center for disabled children. She appeared in several live-action films to promote the project, including The Silk Tree Ballad, Mariko-Mother, and Children Drawing Rainbows. This anime charts the 14-year period of Miyagi's stewardship of the academy and her relationships with several of the children. Divided into four seasonal chapters, the film uses highly realistic character designs based on the actual people involved and features storyboarding from the versatile Star Blazers-director Noboru Ishiguro.

(Source: AnimeVice)