This was the saddest Little Mermaid I ever saw as a child due to the fact it was the actual canon story. Toei Animation got the 'rights' from Hans Christoper Anderson's co relatives to make an animated film annotation of it. This was long before Disney's : The Little Mermaid but gave one of Walts Disney's Co Founders reason to make the Disney version with a happy ending. This was the first little mermaid I saw and might have been the first time I suffer from depression watching this film.
Watch at your own risk if your interested