I saw the short movie named Mermaid by Osamu Teduka. I'll write about this movie.
There are two main characters, a boy and a mermaid. A mermaid is female and a boy probably loves her.
The story happens in the country where daydreaming is forbidden. One day, a boy finds the small fish on the beach. He put it into the pool, then it suddenly becomes a female mermaid. A boy and a mermaid play together in the ocean. After that, he bring her to his house and he put her into the aquarium. He insists to his parents that there is a mermaid in the aquarium, but they don't believe his insistence because they cannot see a mermaid. In addition, he is caught by police by daydreaming and punished with various ways. He can't forget her at first, however he finally forgets her. He is emancipated and runs to his house. He looks at the aquarium, but there is just the fish. He brings it to the ocean and again puts it into water. Then it turns to be a mermaid at the end of this story.
I think this story tells us the importance of believing and the freedom of imagination. Osamu Teduka probably shows us there is no impossible thing in our lives.