It's a story about an imaginative boy who finds a small fish and imagine it as a mermaid. Though, he lives in a country where imagination is prohibited, so the government of the country tortures him to forget about the mermaid. It resulted in him being impossible to remember what it looked like and he struggles, but when he went to the sea again to release the fish, he saw the beautiful mermaid.
I think that the boy will keep visiting the sea by his own to see the mermaid without being found by others.
In this story, I think Tezuka wanted to tell us that no one could actually stop people from imagining things.
