Theory:

Once upon a time, there lived a young woodcutter named Taro. He was poor but kindhearted. He lived with his old parents in an old hut.
 
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A hut similar to Taro's
 
One evening, while the three of them were sitting in their hut, a strong and cold wind blew in. The father shivered badly and wished he had a cup of saké. He felt that the saké would help him feel much warmer.
 
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Saké 
 
But Taro didn't have enough money to buy the saké as it was very costly. He became very sad but decided to work harder and earn more money.
 
The next morning, Taro woke up very early and went to the forest to chop wood. Time went by, but he kept working without any rest. When the sun climbed, he started feeling very hottired, and thirsty. But he kept on working because he had wanted to earn more money.
 
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Taro is feeling very hot because of the sun.
 
Then, all of a sudden, he heard a sound. It was the sound of rushing water. He ran deep into the forest and reached the spot, and it was a waterfall!
 
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The waterfall that Taro's discovered.
 
He drank from the waterfall, but to his surprise, it tasted like saké. He soon collected some of it in his pitcher and hurried back home. He gave it to his father. His father took a sip and became very healthy.
 
In the same afternoon, a lady visited them. Taro's father offered her a cup of saké, and Taro told her the story of the waterfall.
 
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The lady drinking a cup of sake 
 
By the end of the day, the news spread around the village, and everyone visited Taro. They were all eager to taste the drink and hear the story about the magic waterfall. Taro's pitcher of saké became empty by serving it to the guests.
 
The next day, Taro woke up earlier than the previous day. He had planned to go to the waterfall to collect more saké for his father. He took with him the largest pitcher he had at home.
 
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Taro took a large pitcher to collect more saké from the waterfall.
 
But when he reached the waterfall, he discovered that the entire village was there. They had come with all kinds of containers to hold and carry home the saké.
 
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The villagers gathered at the waterfall to collect sake.
 
One of the villagers drank from the waterfall but shouted out that it was only water. Soon, every one tasted it, and they all agreed that it was only water and not saké. They felt tricked and were angry at Taro.
 
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The angry villagers
 
Meanwhile, Taro had slipped behind a rock. He only came out when everyone had left. He went to the waterfall and drank from it. But, to his amazement, it was the saké and not water.
 
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Taro collects some water to taste.
 
The magic waterfall gave saké to Taro but water to everyone else. The waterfall's transformation was a gift to Taro for being a thoughtful and loving son.
 
Soon, the story of Taro and the magic waterfall spread and reached the Emperor of Japan.
 
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The Emperor of Japan learns about Taro and the magic waterfall.
 
He rewarded Taro with \(20\) gold coins. He also gave the waterfall Taro's name.
 
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The emperor rewards Taro with 20 gold coins.
 
The reward was to encourage the children to become good like Taro. Hence, Taro became a role model for all children in Japan.