风吹草动 — “Any slight sign of disturbance or change”

During the Spring and Autumn period, King Ping of Chu was a monarch deeply infatuated with women, to the point of taking his son's fiancée as his own. His minister, Wu She, strongly opposed such behavior. Displeased, King Ping ordered Wu She's arrest, and his eldest son was also executed.

However, Wu She's second son, Wu Zixu, realizing the dire situation, quickly fled for his life. Along the way, he constantly hid, terrified by any 'wind blowing and grass moving' (风吹草动) – the slightest sound or movement would send shivers down his spine.

One day, Wu Zixu arrived at a riverbank and met an old fisherman, to whom he recounted the entire truth of his plight. Later, the fisherman went ashore to find food for him. Wu Zixu, fearing betrayal, hid himself among the reeds by the bank. When the fisherman returned and found him gone, he called out to reassure him, telling him not to worry and to come out quickly to enjoy a hearty meal. Before Wu Zixu departed, he specifically cautioned the fisherman never to reveal that he had seen him. The fisherman, seeing Wu Zixu's suspicion, and to put his mind at ease, tragically jumped into the river and drowned.

Deeply saddened, Wu Zixu continued his escape. Eventually, he gained significant trust and power in the Kingdom of Wu, taking command of their army. He immediately launched an attack on Chu, successfully avenging the murder of his father.