The main characters
The fish (mermaid) and the boy
Plot
The boy found a fish at the shore, and the boy had a wild imagination that made the fish appear as if it was a mermaid. He spent a joyful time with her and took her back to his house. He showed his parents his new friend but they only saw her as a fish. Since the government? restricted excess imagination, the boy was confined and tortured until the mermaid returned to a fish, meaning the boy lost his imagination.
Ending
The boy kept is identity and at the end the boy saw the mermaid again
opinion: Tezuka Osamu sketched the situation in 1960 through this animation describing it as a era where people were controlled by the government and restricted of there freedom.