Tezuka, O. (1965). Mermaid.
Main Characters
A boy and a fish (mermaid)
Plot
A boy found a fish at the beach and imagined it was a mermaid. He told the adults about the mermaid but the country he lived didn't allow to imagine so he was tortured to forget such fantasies. Last, he came back home but could not remember the mermaid and goes to the beach again.
Ending
He died, or at least his soul died and he was free to be in his imaginary world again.
The message of this film
It is impossible not to imagine, nor to think something what the government does not like.