Xiao Sa was originally a stray civet cat in the palace. Through years of hard work, he became the "cat boss". He often observed on the roof of the palace at night and knew many secrets. He was saved by the Seventh Prince. When the Seventh Prince fell into the water and was dying, he was sucked into his body by a mysterious force due to his touch. From then on, he lived as the Seventh Prince. Retaining the characteristics of a cat, he is agile in speed, has strong climbing ability, and is good at catching fish. Later, he learned to solve cases from his uncle, the Minister of Civil Affairs, and gradually grew into a great man.
