Once upon a time, there lived a god. God told the animals living there to come and greet him on January 1.
God told them that the first to twelfth animal that came to greet him on that day would be the animal of the year. Hearing this, the animals set out in high spirits to somehow become the animal of the year. However, the cat got careless and forgot when to go to God. The cat was so puzzled that it went to the mouse to ask him.
On January 1, the mouse was the first to go to God. However, the cat, tricked by the mouse, arrived the next day and was not the first animal to reach God. After this incident, the cat and the mouse did not get along well.

This is the story. However, this is only a made-up story, and this is not the real reason.
So what is the real reason? Unfortunately, this is not clearly known. The twelve signs of the Chinese zodiac were created in ancient China. Of course, it is not that there were no cats in ancient China. On the contrary, cats were very familiar creatures in China. It is a real mystery why cats were not included in the twelve Chinese zodiac signs.
The ancient people must have thought up this story because they did not know the reason.