Saddest movie ever: Helen the Baby Fox

From Variety:

Seven-year old Taichi (Arashi Fukasawa) is shunted to the remote Hokkaido home of a veterinarian (Takao Osawa) when his camerawoman mom travels on a Pacific photographic assignment. Feeling neglected, the tyke takes pity on a deaf, blind, mute fox he names after Helen Keller. This guardian role teaches Taichi about parental responsibilities and sharpens his appreciation of his career mom's duty to make a living for both their benefits.